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by an assiduous observer for twenty-seven years. It is this, however, and much more; and Mr. Prince must be congratulated upon having written a very interesting and readable book upon what we fear would, in the hands of most men, be a very dry subject. The observations he has collected show what valuable information might be stored up by many country surgeons, clergymen, and farmers, at little cost of time or money, by adopting a regular system. The parish of Uckfield, Mr. Prince tells us, lies upon an undulatory tract of country situated about midway between the South Downs and the highest point of Ashdown Forest. The upper portion of the town is 200 feet, and the lower 66 feet, above the level of the sea. It is situated on the Horsted beds of the Hastings Sands. The instruments were read every morning at nine o'clock. The annual mean height of the barometer at Uckfield, as deduced from observations extending over seventeen years, was 29'982 in. Mr. Prince gives the mean temperature of winter at Uckfield from all his observations at 38° 96 Fahr.; of spring at 47°.66; of summer at 61°34, and of autumn at 50°45. The coldest winter was that of 1845; the warmest that of 1869; the difference being 1099. The coldest spring was that of 1845; the warmest that of 1848; the difference, 5°84. The coldest summer was that of 1860; the warmest that of 1859; the difference being 6° 74. The coldest autumn was that of 1867; the warmest that of 1857; the difference being 6°22.

Mr. Prince points out that "the mean annual temperature varies 53, viz.: from 51°93 in 1857 to 46°62 in 1845, and although at first sight this difference may not appear considerable, yet it is sufficient to exert an enormous influence upon the general character of the seasons, the produce of the soil, and the health of the population. The Registrar-General's interesting returns have fully established the important fact that there is a very intimate connection between temperature and mortality. Whenever the mean temperature falls to 45°, or thereabouts, the number of deaths from diseases of the respiratory organs increases, and should it fall below 40°, death-rate from such diseases is still higher. When a period of intense cold prevails, so that the temperature scarcely rises above the freezing point for two or three weeks, the number of deaths will be found to exceed what takes place during an epidemic of cholera or scarlet fever. But when the mean temperature rises to 55°, there will be an increase in the number of deaths from diseases of the abdominal viscera, and this number will fluctuate as the temperature fluctuates between 55° and 65°. Hence we are informed that the mortality from all causes is least when the temperature is about 50°, which is very little above our mean annual temperature." In this way Mr. Prince deduces important conclusions from statistics, and renders his book much lighter reading than might have been anticipated. He devotes a chapter to the general characters of the months, and then inserts a series of monthly remarks respecting atmospheric phenomena from the year 1843 to 1870, both inclusive. His fifth chapter treats of prognostics of atmospheric changes, and includes a translation of the poet Aratus' "Diosemeia." He remarks very sensibly that with reference to prognostics of seasons, there are very few upon which any reliance can be placed. But the following, of which we can only quote a few, need not, he thinks, be altogether discarded.

From whatever quarter the wind blows at the quarter days, there is a probability of its being the prevalent wind during the ensuing quarter. Whenever the latter part of February and beginning of March are dry, there will be a deficiency of rain up to Midsummer-day. When the foliage of the ash appears before that of the oak, we shall probably have much rain the first half of the summer; but there will be a good harvest-time. When during the spring more swifts than swallows arrive, expect a hot and dry summer. Many other prognostics of change of weather are given, drawn from the habits of mammals,

birds, insects, and plants, some of which are very curious.

The last chapter gives some vital statistics in regard to the population of the country; from which it appears that Sussex is one of the most salubrious counties in England, its death-rate being 182 per cent., in which it is surpassed only by the extra-Metropolitan portion of Surrey, the mortality of which is only 178; whilst that of Lancashire is 278 per cent. Upon the whole we warmly recommend Mr. Prince's book to our readers, and trust that some of them may be induced to commence a similar series of observations. A flora of the district, with the times of flowering of the plants, would, we think, be an interesting addition to Mr. Prince's work. H. P.

LETTERS TO THE EDITOR

[The Editor does not hold himself responsible for opinions expressed by his correspondents. No notice is taken of anonymous communications.]

area.

Circumpolar Land

In a previous letter* I have endeavoured to show that the land surrounding the North Pole is rising in a continuous and definite I find that what I there said about the land north of America is very scanty and unsatisfactory, and before proceed. ing to the next part of my subject, I wish to strengthen it somewhat. Speaking of the eastern part of Melville Island, Captain Parry says one of the Hecla's men brought to the boat a narwhal horn, which he found on a hill more than a mile from the sea. Sergeant Martin and Captain Sabine's servant brought down to the beach several pieces of fir tree, which they found nearly buried in the sand, at the distance of 300 or 400 yards from the present high-water mark, and not less than thirty feet above the sea level (Parry's Voyage, 1819, 1820, p. 68). Again, “in the north of Melville Island, two pieces of drift wood were found, ten or twenty feet above the present sea level, and both partly buried in the sand" (p. 193). Again, speaking of west of the same island, "The land gains upon the sea, as it is called, in process of time, as it has certainly done here, from the situation in which we found the drift wood and the skeletons of whales"

(Pranklin's voyage in 1819, 20, and 21, he mentions having

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66

found much drift wood in the estuary of the Copper Mine River. He also picked up 66 some decayed wood far out of reach of the water (see his narrative, p. 357). In his second voyage along the Arctic Sea, he describes the coast from the Mackenzie River to the Rocky Mountains as very shallow, and full of shoals and reefs. Inside some of the latter was brackish water, as was also the water in pools at some distance inland; piles of wood were also thrown up far from the coast (see p. 134). While Franklin surveyed the coast westward, Dr. Richardson did the same to the east. He says, On the coast from Cape Lyon to Point Keats, there is a line of large drift timber, evidently thrown up by the waves, about twelve feet in perpendicular height above the or He shortly afterwards mentions that in the dinary spring tides.” Polar Sea, when cumbered with ice, such waves are impossible, and as his journey was in the hottest season, and the sea was then crowded with hummocks, the inference that the drift wood was thrown up by the waves is inadmissible; and the line of drift wood twelve feet above the sea level is only a parallel to the numerous cases we have mentioned. The vast sheet of shallow and brackish water, 140 miles long and 150 broad, which is separated from the Polar Sea by low banks and spits of sand, and is called by Dr. Richardson Esquimaux Lake, formed, there can be little doubt, very recently, as that traveller suggested, a bay of the Polar Sea, and is an example of the formation of huge brackish lakes by a sea which is constantly contracting, such as are so familiar in the eastern borders of the Caspian. collect the many instances of the same kind that are found in the It would be impossible, in the short space at my command, to later Arctic voyages; but I would especially commend the pages of Captain Maclure's and of Sir Edward Belcher's narratives, as containing very striking ones.

The orthodox school of physical geographers generally speak * See NATURE, vol. v., p: 163.

of Behring's Straits, and the shallow sea about the islands, as an area of depression, but without any authority, so far as I know.

Those barren and desolate islands, so well described by the Russians, bear all the traces of having recently been under water, and the American Birkbeck has proved, beyond much doubt, that the eastern coasts of Asia, including China and Japan, are being upheaved. I find I was forestalled by Pennant in the conjecture of the very recent junction of the White Sea and the Baltic, and I am very glad to quote him as an authority. He says the lakes Sig, Ondar, and Wigo, form successive links from the Lake Onega to the White Sea. The Lake Saima almost cuts Finland through from north to south; its northern end is not remote from Lake Onda, and the southern extends very near to the Gulf of Finland, a space of nearly 40 Swedish or 260 English miles. These, probably, were part of the bed of the ancient Streights (sic) which joined the White and Baltic Seas (Appendix to Arctic Zoology, 23).

In regard to the rise of Spitzbergen, it is curious to find the following passage so early as 1646 :-"These mountains (twentytwo mountains of Spitzbergen) increase in bulk every year, so as to be plainly discovered by those that pass that way. Leonin was not a little surprised to discover upon one of these hills about a league from the sea-side, a small mast or a ship, with one of its pullies still fastened to it; this made him ask the seamen how that mast came there, who told him they were not able to tell, but were sure they had seen it as long as they had used that coast. Perhaps, formerly, the sea might either cover or come near their mountain, where some ship or other being stranded, this mast is some remnant of that wreck." (Account of Greenland by M. La Peyrere in Churchill's Voyages, vol. ii.) Parry, in his account of his journey towards the Pole, 126, also refers to the vast quantities of drift wood stranded on the Spitzbergen coasts above high-water mark.

Having strengthened my former paper by instances of upheaval in other points, and I hope satisfied your readers of the justice of the generalisation about the rise of circumpolar land, it is natural to ask if this remarkable fact is paralleled in any way at the southern pole,-whether we can show that both in the Arctic and Antarctic seas there is a bulging out of the land, and a displacement of the sea at present in progress. Our knowledge of the lands immediately about the southern pole is very scanty; but fortunately we have unmistakeable evidence at the various points of those better known austral lands which approach the antarctic seas, from which we may be justified in drawing a sound conclusion, South America, New Zealand, Australia, Tasmania, and Southern Africa.

To begin with South America, I cannot quote a better authority than Mr. Darwin :

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Everything in this southern continent has been effected on a grand scale: the land from the Rio Plata to Terra del Fuego, a distance of 1,200 miles, has been raised in mass (and in Patagonia to a height of between 300 and 400 feet) within the period of the now-existing sea shells. The old and weathered shells left on the surface of the upraised plain still partially retain their colours. I have said that within the period of existing sea shells, Patagonia has been raised 300 to 400 feet; I may add that within the period when icebergs transported boulders over the upper plain of Santa Cruz the elevation has been at least 1,500 feet" (Naturalists' Voyage p. 171). Again, "M. d'Orbigny found on the banks of the Parana, at the height of 100 feet, great beds of an estuary shell now living 100 miles lower down nearer the sea, and I found similar shells at a less height on the banks of the Uruguay; this shows that just before the Pampas was slowly elevated into dry land the water covering it was brackish. Below Buenos Ayres there are upraised beds of sea-shells of existing species, which also proves that the period of elevation of the Pampas was within the recent period" (p. 130). So much for the East Coast. Now for the West. Speaking of the Hacienda of Quintero, in Central Chili, he says:-"The proofs of the elevation of this whole line of coast are unequivocal. At the height of a few hundred feet old-looking shells are very numerous." Again, speaking of Northern Chili, he says:"I have convincing proofs that this part of the continent of South America has been elevated near the coast at least from 400 to 500 feet, and in some parts from 1,000 to 1,300 feet, since the epoch of existing shells, and further inland the rise may have been greater." In Peru, about Callao, he also found evidences of rising land; but here we come to one of the horizons where rising and sinking land meet. If it be necessary to supplement the account

of Mr. Darwin, I have the authority of Mr. Baxendall for stating that he found numerous skeletons of whales and seals stranded above high-water mark on the coast near Africa, where a tide (as is well known to be the case in all the Eastern Pacific) is almost unknown.'

Having satisfied ourselves of the rise of the southern portion of South America, we must now shortly state the reasons for making it very recent. Speaking of the earthquake of 1822, which caused a general upheaval of the land, Mr. Darwin says, "The most remarkable effect of this earthquake was the permanent elevation of the land; the land round the Bay of Conception was upraised two or three feet, at the island of Santa Maria (about thirty miles distant) the elevation was greater. On one part Captain FitzRoy found beds of putrid mussel-shells still adhering to the rocks 10 feet above high water-mark; the inhabitants had formerly dived at low-water spring tides for these shells" (p. 310). Again, two years and three-quarters afterwards Valdivia and Chiloe were again shaken, and an island in the Chonos Archipelago was permanently elevated more than 8 feet. At Valparaiso within the last 220 years the rise has been somewhat less than 19 feet, while at Lima a sea beach has certainly been upheaved from 80 to 90 feet within the Indo-human period (id. passim). Eighty-five feet above the sea level in an island in the Bay of Callao he found on a sea beach some Indian corn and pieces of Indian thread, similar to those found in Peruvian tombs, a parallel find to that made by Sir Charles Lyell in Scandinavia, which I previously referred to.

Having examined the evidence for South America, we will now turn to the other great southern continent, Africa. I will quote a few passages. "There cannot be the slightest doubt that the upheaval of the country is still going on; for along the whole coast of South Africa from the Cape to Durham Bluff, and still farther north, even as far as Zanzibar, modern raised beaches, coral reefs, and oyster banks may everywhere be seen. At the Izinhluzabalungu Caves is such a point, where the rising of the coast is plainly visible, recent oyster-shells are now 12 feet and more above high-water mark. The same can be observed on the whole line of the Natal Coast. Van der Decken has observed the same thing at Zanzibar, and is of the same opinion as myself, viz., that the Eastern Coast is rising early in the present year (ie., 1870). I had the opportunity of observing at the Bazanito Islands about ninety miles north of Inhambane, on the east coast of Africa, a series of raised coral reefs round the island of Marsha containing many living shells and quite recent oyster-banks." (Griesbach, Geology of Natal, Quart. Journ. Geol. Soc. xxvii. part ii. p. 69.) Mr. Griesbach also mentions that he saw implements of early man, which were obtained by Richard Thornton and others in old raised beaches of Natal, near Inanda, and at the mouth of the Zambesi River.

Mr. Griesbach is confirmed by Mr. Stow in his papers on the Geology of South Africa in the same Journal (see vol. xxvii. p. 526 et seq.), where bones and teeth are found mixed with shells, quite in a recent state, about Port Elizabeth, &c.

In regard to Tasmania, I quote the following from Mr. Wintle's paper on the Geology of Hobart Town (Mine Journal, vol. xxvii. P. 469):-"Until a very recent period in the geological annals of this island, a great portion of what now constitutes the site of this city was under water. This is proved by the extensive deposits of comminuted shells, all of recent species, which are met with for miles along the banks of the Derwent. Some of these deposits are at an elevation of upwards of 100 feet above high-water mark, and from 50 to 100 yards from the water's edge, plainly showing thereby that a very recent elevation of the land has taken place." M. Reclus says

In New Zealand the evidence is the same. the port of Lyttelton has risen 3 feet since it was occupied by the settlers. Mr. Forbes says that proofs of upheaving of the land are even now obvious to any intelligent traveller. Some of these changes have been witnessed by the present generation. Again, in the Middle Island upheaval of the land is observable in a marked manner through the entire length of the western coast from Cape Farewell to Dusky Bay. Some of the most extraordinary changes in these regions have taken place within the last few years.

This has been confirmed by Dr. Haast, who, however, found some signs of depression at the north-western extremity of the lands. In Australia our evidence is ample:-The north-east, if not the whole of the east coast of Australia, is slowly rising, as proved by the gradual shoaling of the Channel between Hinchinbrook Island and the mainland, due to all appearance neither to

silting up nor growth of coral water-worn caves, now well above high-water mark in the sandstone cliffs of Albany Island, and those of the mainland opposite, and in the existence along many parts of the coast, especially towards the north of the peninsula, of extensive tracts of level country now covered with sand dunes, bearing a scanty vegetation, stretching inland 10, 15, and 20 miles off, but which once bordered the sea" (Rattray, Geology of Cape York Peninsula, Australia, Mine Journal, vol. xxv. p. 297).

66 An immense portion of the continent of Australia is known to be uprising. The whole coast round to a distance of several miles inland is covered with recent shells; the drainage of the country is apparently altering. Lakes known to have been formerly filled with salt water are now filling up with fresh or becoming dry. The lagoons near the coast are filled with salt and brackish water, and their banks are filled with marine shells with their colours in many cases preserved. Reefs of rocks are constantly appearing in places where there were none formerly. At Rivoli Bay the soundings have altered so much as to make a new survey requisite. A reef has lately almost closed this harbour. Other reefs have appeared at Cape Jaffa, &c. It would appear that a vast movement is taking place in the whole of the south of Australia. In Melbourne the observations of surveyors and engineers have all tended to confirm this remarkable fact. In Western Australia the same thing is observed at King George's Sound, the same," &c., &c., and so on, for many pages. (See Wood's Geological Observations, in South Australia, 135-207, and passim.)

The facts I have enumerated, which might be almost indefinitely multiplied, are sufficient to prove the position that every large mass of land near the South Pole which we can examine shows signs of upheaval, and justifies the conclusion that the circumpolar land is rising at both poles, and that there is a general thrusting out of the earth's periphery in the direction of

its shorter axis.

I must modify the opinion expressed in a previous paper that the 57th parallel is the southern limit of upheaval in the northern hemisphere. The limit of upheaval is an irregular line. I believe that the district intervening between the two projecting poles, with its focus along the equator, is an area of subsidence.

This conclusion I believe to be of crucial importance in solving both geological and meteorological problems.

New Zealand Trees

H. H. HOWORTH

I HAVE been greatly astonished by the perusal of a paragraph on New Zealand timber trees, which appears on p. 14 of the current volume of NATURE (No. 105, Nov. 2, 1871). Almost all that is said, either directly or inferentially in that paragraph is so grossly inaccurate that I cannot understand how such statements found their way into a periodical like yours. In the first place, the Rimu (Dacrydium cupressinum), the Matai (Podocarpus spicata), and the Totara (P. totara), are spoken of as if peculiar to the North Island, whilst the truth is that they are common to all parts of New Zealand. These trees are never "cut down wholesale" for firewood, except perhaps now and then when bush land is being cleared so far from other settlements that transport of the timber to any market is a physical impossibility. The woods enumerated are, Kauri (Dammaris australis), and the white pine (Podocarpus dacrydioides), the principal building timbers of the colony. The Rimu is not "valuable for furniture and all ornamental work," although some choice sections of it look well when carefully polished. Totara and Kauri look better when polished, but their brittleness spoils their usefulness for ordinary furniture work. When I deny that these timbers are "valuable" for cabinet work, I mean that they have not, and never will have, the value which attaches to mahogany, rosewood, walnut, and similar woods. That the Rimu, Matai, and Totara "are none of them Coniferæ," is news to botanists on this side the world. All these trees are to be found in horticultural collections in England and Scotland, and it is to be regretted that the writer of this paragraph did not acquaint himself with them before he undertook to instruct others as to their botanical characteristics. But the most amazing of all the statements in this paragraph is that about the Rata (Metrosideros lucida). This appears to have been quoted from somewhere. I should very much like to know who is responsible for such a monstrous fiction. I can only conceive that its author has confused the Akakura (Metrosideros scandens) with the Rata

in his memory-he could never have confused the objects themselves when before his eyes. The whole story of the manner of growth of the Rata is utterly without foundation.

I may take this opportunity of mentioning that the description of M. lucida in Hooker's "Handbook of the New Zealand Flora" is inaccurate. The tree is there described as a small one, whereas it grows in the South Island to the dimensions of a large forest tree. Probably Dr. Hooker had to depend on informa. tion derived from North Island sources only. W. Dunedin, N. Z., January 13

Earthquakes in the Philippine Islands

IN the middle of December, 1871, the volcano Albay in the S.E. of Luzon began to play, and threw out smoke, stones, and lava for several weeks.

The following phenomena have also to be recorded :1871.-October 8 and 9, at Pollok on Mindanao, sulphurous springs arose in the neighbourhood.

December 8 to 14, at Kottabato on Mindanao, very heavy earthquakes, which destroyed all the houses. from E. to W., which I witnesed. 1872. January 29, at 7 P. M., at Manila, three slight shocks Manila, Feb. 5 A. B. MEYER

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1. Observations to be made at the exact hours and half hours, Greenwich mean time.

line should be noted with reference to the stars; or else its alti2. If there is an arch, the position of the apex of its central mately. If the lower or the upper edge of the arch is well tude should be ascertained carefully, and its azimuth approxidefined, give similar particulars respecting it. State the width what irregular, instead of its actual position, give that of an of the arch; state whether it is regular or not. If it is someimaginary arch having its average position.

3. If there is any other very conspicuous feature, its position among the stars may be observed; care being taken to describe it sufficiently for it to be recognised in any account from another place. But the position of the corona, or point to which the rays converge, is of no value for determining the height of the aurora, for it is merely an apparent phenomenon.

Observers must not consider themselves tied down to observe on every occasion; any observations, if made in accordance with these rules, may be useful. If they are sent to me, I will endeavour to calculate the aurora's height from them, unless some one else volunteers to take them in hand.

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IN Mr. Monck's article on barometric variations in NATURE of 21st inst. there is a serious mistake about the theory of tradewinds. He says the trade-winds would probably extend to the poles were it not that the parallels of latitude become so narrow before reaching them. The trade-winds are east winds; and if, as is certainly the case, the only motive power acting on the earth's atmosphere is the sun's heat, it follows from the law of the conservation of rotation that the total force of the east and west winds must exactly balance each other. This must be the case even were the earth of some other form than a sphere. JOSEPH JOHN MURPHY

Old Forge, Dunmurry, March 25

FURTHER INVESTIGATIONS ON PLANETARY INFLUENCE UPON SOLAR ACTIVITY*

I.

IN

Na previous communication by us to this Society, an abstract of which was published in the Proceedings, vol. xiv. p. 59,† we showed some grounds for believing that the behaviour of sun-spots with regard to increase and diminution, as they pass across the sun's visible disc, is not altogether of an arbitrary nature. From the information which we then had, we were led to think that during a period of several months sun-spots will, on the whole, attain their minimum of size at the centre of the disc. They will then alter their behaviour so as, on the whole, to diminish during the whole time of their passage across the disc; thirdly, their behaviour will be such that they reach a maximum at the centre; and, lastly, they will be found to increase in size during their whole passage across the disc. These various types of behaviour appear to us always to follow one another in the above order; and in a paper printed for private circulation in 1866, we discussed the matter at considerable length, after having carefully measured the area of each of the groups observed by Carrington, in order to increase the accuracy of our results. In this paper we obtained nineteen or twenty months as the approximate value of the period of recurrence of the same behaviour. 2. A recurrence of this kind is rather a deduction from observations more or less probable than an hypothesis ; nevertheless, it appeared to us to connect itself at once with an hypothesis regarding sun-spot activity. "The average size of a spot" (we remarked) "would appear to attain its maximum on that side of the sun which is turned away from Venus, and to have its minimum in the neighbourhood of this planet." In venturing a remark of this nature, we were aware it might be said," How can a comparatively small body like one of the planets so far away from the sun cause such enormous disturbances on the sun's surface as we know sun-spots to be?" It ought, however, we think, to be borne in mind that in sun-spots we have, as a matter of fact, a set of phenomena curiously restricted to certain solar latitudes, within which, however, they vary according to some complicated periodical law, and presenting also periodical variations in their frequency of a strangely complicated nature. Now these phenomena must either be caused by something within the sun's surface, or by something without it. But if we cannot easily imagine bodies so distant as the planets to produce such large effects, we have equal difficulty in imagining anything beneath the sun's surface that could give rise to phenomena of such a complicated periodicity. Nevertheless, as we have remarked, sun-spots do exist, and obey complicated laws, whether they be caused by something within or something without the sun. Under these circumstances, it does not appear to us unphilosophical to see whether as a matter of fact the behaviour of sun-spots has any reference to planetary positions. There likewise appears to be this advantage in establishing a connection of any kind between the behaviour of sun-spots and the positions of some one prominent planet, that we at once expect a similar result in the case of another planet of nearly equal prominence, and are thus led to use our idea as a working hypothesis.

3. We have now a larger number of observations at our disposal than we had in 1866. We had then only the groups observed by Carrington, the positions and areas of all of which we had accurately measured. We have now in addition five years of the Kew observations, for each group of which the positions and areas have been recorded

By Warren De La Rue, D.C.L., F.R.S., Balfour Stewart, LL.D., F.R.S., and Benjamin Loewy, F.R.A. S. Read before the Royal Society, March 14, 1872.

↑ See NATURE, vol. v., p. 192.

by us in our previous communications to this society. We have thus altogether observations extending from the beginning of 1854 to the end of 1860, forming the series of Carrington; and observations extending from the beginning of 1866, forming the Kew series, as far as this is yet reduced. We have, in fact, altogether a nearly continuous series, beginning a year or two before one minimum, and extending to the next, and thus embracing rather more than a whole period.

We propose in the following pages to discuss the behaviour with regard to size of the various groups of these two series, as each group passes from left to right across the sun's visible disc. Unfortunately for this purpose, a large number of groups has to be rejected; for, on account of bad weather, we have frequent blank days, cannot be seen, and on this during which the sun account we cannot tell with sufficient accuracy the behaviour of many groups as they pass across the disc. In our catalogue of sun-spot behaviour, we have only retained those groups for which, making the times abscissæ, and the areas ordinates, we had sufficiently frequent observations to enable us to construct a reasonably accurate curve exhibiting the area of the group for each point of its passage across the disc. From these curves a table was then formed denoting the probable area of each non-rejected group at the following heliographic longitudes (that of the visible centre of the disc being reckoned as zero) :—

-

- 63° - 49° - 35° − 21° −7°+7°+21°+35° +49°+63° ; in fact, giving the area of the group for the ten central days of its progress, and rejecting those observations that were too near the sun's border on either side, on account of the uncertainty of measurement of such observations. We have succeeded in tabulating in this manner 421 groups of Carrington's series, and 373 groups of the Kew series up to the end of 1866, in all 794 groups. In this catalogue the area is that of the whole spot, including umbra and penumbra; and in measuring these areas a correction for foreshortening has always been made, as described in a paper which we presented to this society, and which constitutes the first series of our researches. These areas are expressed in millionths of the sun's visible hemisphere.

4. When we began this present investigation into the behaviour of spots, we soon found reason to conclude that in the case of sun-spots the usual formula for foreshortening is not strictly correct. Perhaps if a sun-spot were strictly a surface-phenomenon, the usual formula might be correct, though even that is doubtful; for the earth as a planet may not impossibly affect the behaviour of all spots as they cross the disc, so as to render the formula somewhat inexact. However this may be, a spot is probably always surrounded more or less by faculous matter, forming in many cases a sort of cylindrical wall round the spot. Now the effect of such a wall would be to allow the whole spot to be seen when at or near the centre of the disc, but to hide part of the spot as it approached the border on either side. A spot thus affected would therefore appear to be more diminished by foreshortening than the usual formula would indicate; and we should therefore expect, if this were the case, that, on the whole, after making the usual allowance for foreshortening, spots would nevertheless be found deficient in area near the borders as compared with their area at the centre of the disc. As a matter of fact we have something of this kind, as will be seen from the following table, in which we have used the whole body of spots forming the catalogue to which we have made allusion.

In this table the first column denotes the heliocentric longitude from the centre of the disc reckoned as zero; the second denotes the united areas at the various longitudes of all those groups from both series, the behaviour

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5. From the above table it appears that the average behaviour of spots, as far as can be judged from the information at present attainable, is not quite symmetrical as regards the centre of the disc. Without attempting at present to enter into an explanation of this remarkable phenomenon, we may point to it as a confirmation of our view previously stated, that most spots are accompanied by a wall-shaped surrounding of facula. Observations show that on the whole the life-history of the facula begins and ends earlier than that of the spot which it surrounds, and that throughout a gradual subsidence of this elevated mural appendage seems to be taking place. But such a diminution of the wall discloses more of the spot itself, and hence the spot-areas, measured on the eastern half of the hemisphere, might be expected, cæteris paribus, to be smaller than those observed in the western half, a fact strikingly demonstrated by the above table.

Our present object, however, is not to account for the average behaviour of spots, but rather to investigate the causes or concomitants of a departure from this average behaviour. We have, therefore, in all cases made use of the factors given in the above table as those which, judging by the average behaviour, tend to equalise the

areas that pass the various longitudes. We have called this earth-correction, and have limited our discussion to any well-marked behaviour that remains after the earthcorrection has been applied.

Let us now divide the whole mass of observations into four portions, depending upon the position of the planet Venus with reference to the earth or point of view. First, let us take each occasion on which the planet is in the same heliographic longitude as the earth, that is to say, when the earth and Venus are nearly in a line on the same side of the sun.

Let us use five months' observations for each such occasion, extending equally on both sides of it; thus, for instance, if the planet Venus and the earth had the same heliocentric longitude on September 30, 1855, we should make use of sun-spots from the middle of July to the middle of December of that year as likely to represent any behaviour that might be due to this particular posi tion of Venus. Let us do the same for all similar occa. sions, and finally add all the spots thus selected together. We have thus obtained a mass of observations which may be supposed to represent any behaviour due to this position of the planet Venus with reference to the earth or point of view.

Secondly, let us now take each occasion on which Venus is at the same longitude as the extreme right of the visible disc, that is to say, 90° before the earth, and do the same as we did in the previous instance, using five months' observations for each occasion We shall thus, as before, obtain a mass of observations which may be supposed to represent the behaviour due to a position of Venus 90° before the earth. Thirdly, let us obtain in a similar manner a mass of observations representing the behaviour of sun-spots for a position of Venus 180° before the earth, Venus and the earth being now at exactly opposite sides of the sun; and fourthly, let us finally obtain, in a similar manner, those observations representing the behaviour of sun-spots when Venus is 270° before the earth, being now of the same heliocentric longitude as the extreme left of the visible disc.

These four series of five months each will in fact split up the whole body of observations into four equal parts, the synodical revolution of Venus being nearly twenty months. The following table exhibits these series after the earth-correction has been applied to each. It also represents each series reduced so as to exhibit its characteristic behaviour for an average size of spot = 1000,

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