Report (referred to in last week's NATURE) on application to the Hon. Secretaries, King Edward's School, Birmingham, or to the London Local Secretaries, Mr. C. W. Merrifield, F. R.S., South Kensington, and Mr. R. Tucker, University College School.

MR. I. LOWTHIAN BELL read a paper at the Institution of Civil Engineers on Tuesday evening, March 18, "On the conditions which favour and those which limit the Economy of Fuel in the Blast Furnace for Smelting Iron." A discussion on the paper was taken at the following meeting on Tuesday evening

last.

:

MR. ALFRED SMEE, F. R. S., has in the press a volume entitled My Garden, in which he gives a complete description of his experimental garden at Beddington, in Surrey, and details the results of his experience in the culture of flowers and fruit of these nearly 700 species and genera are described. The volume also treats generally of the natural history, geology, and antiquities of the neighbourhood. It is illustrated with about 1,cco wood engravings, executed expressly for the work. The volume will be published by Messrs. Bell and Daldy.

But,

ANNUAL ADDRESS TO THE GEOLOGICAL SOCIETY OF LONDON, FEB. 16, 1872 BY J. PRESTWICH, F.R.S., PRESIDENT IN looking at the labours of the Society during the past year, it is satisfactory to notice the same activity, the same wide range of subjects as ever, and the same independence of research for truth's sake which there ever should be. though good work has been done in special branches and the technical details of Geology, not so much progress has been made in its higher problems. I would, however, direct your attention to the steps made in grouping our volcanic rocks, and in the determination of the fauna of our Cambrian strata, which proves to be so much larger and richer than was anticipated a few years back. Both these subjects are in able hands, and can. not fail to yield important results, the latter especially in aiding to settle that interesting question-the true line of division between the Silurian and the Cambrian formations. On the subject of denudation and river-action, we have also had several excellent papers, and look forward with interest to the further development of the many original views which they have put before us.

The great question of the history of our globe during the Quaternary period seems also to be advancing towards more completeness. Many able observers, both in and out of our own Society, are engaged upon the subject, and various scientific periodicals and publications of our local societies are rich in contributions bearing upon this interesting subject. There is no more wonderful chapter in the earth's history than that which embraces the phenomena connected with the prevalence of great and exceptional cold immediately preceding our time, -the first dim appearance of man-his association with a race of great extinct Mammalia belonging to a cold climate-the persistent zoological characters of the one, so far as we have yet gone, in opposition to the variable types presented in geological time by the othersthe search for connecting links, and the measure of man's antiquity, all of which constitute theoretical problems of the highest interest, and are now occupying the attention of geologists of all countries. Allied also to this subject are the great questions relating to the form of our present continents-the elevation of the land-the origin of valleys and plains-and of all that which prepared this globe for the advent of man.

But while treating of these abstract and philosophical questions, geology deals also with the requirements of civilised man, showing him the best mode of providing for many of his wants, and guiding him in the search of much that is necessary for his welfare. The questions of water-supply, of building materials, of metalliferous veins, of iron and coal-supply, and of surfacesoils, all come under this head, and constitute a scarcely less important, although a more special branch of our science than the paleontological questions connected with the life of past periods, or than the great theoretical problems relating to physical and cosmical phenomena. Looking at this triple division of geology, and seeing that the first, or applied geology, is, as it were, only

incidental to our general studies, and therefore not often the topic of our discussions, notwithstanding its practical importance, I propose on this occasion to say a few words in connection with the two momentous subjects which, during the last few years, have been made the objects of investigation by two Royal Com missions, on both of which the geological questions have received much and careful consideration. I shall here restrict myself to the more special geological bearings of the subject, extending them, however, in some directions beyond the scope of the original inquiries, and refer you to the Reports and Minutes of Evidence themselves for the many valuable economical questions and practical details which are there discussed.

Our Springs and Water-supply.

The site of a spring or the presence of a stream determined probably the first settlements of savage man; and his civilised descendants have continued, until the last few years, equally dependent upon like conditions-conditions connected first with the rainfall, and, secondly, with the distribution of the permeable and impermeable strata forming the surface of the country. Under ordinary circumstances, few large towns have arisen except where there has been an easily accessible localised water-supply, and where the catchment-basin on which depends the volume of the rivers has been large, and permeable strata prevail. Take, for example, London. Few sites could be more favourable in every respect. Beneath it are strata rich in springs, while at a distance there is that large development of those massive permeable strata so necessary to maintain a sufficient and permanent flow in our rivers. As the conditions exhibited in the London basin afford all the illustrations we need for our subject, I will confine myself in this address to that area alone.

London north of the Thames stands on a bed of gravel, varying in thickness from ten to twenty feet in round numbers, and overlying strata of tenacious clay from 100 to 200 feet. The former being easily permeable, the rain falling on its surface filters through it, until stopped by the impermeable London clay, where it accumulates and forms a never-failing source of supply to the innumerable shallow wells that have been sunk all over London from time immemorial, and which for centuries constituted its sole watersupply. Not only does it form an easily accessible underground reservoir, although of limited dimensions; but where the small intersecting valleys cut down through the bed of gravel into the London clay, a portion of the water in this reservoir escapes at the junction of the two strata, and gives rise to several springs formerly in much repute, such as those of Bagnigge Well, Holywell, Clerken-well, St. Chad's Well, and others.

The early growth of London followed unerringly the direction of this bed of gravel, eastward towards Whitechapel, Bow, and Stepney; north-eastward towards Hackney, Clapton, and Newington; and westward towards Chelsea and Kensington; while northward it came for many years to a sudden termination at Clerkenwell, Bloomsbury, Marylebone, Paddington, and Bayswater; for north of a line drawn from Bayswater by the Great Western station, Clarence Gate, Park Square, and along the north side of the New Road to Euston Square, Burton Crescent, and Mecklenburg Square, this bed of gravel terminates abruptly, and the London clay comes to the surface, and occupies all the ground to the north. A map of London, so recent as 1817, shows how well-defined was the extension of houses arising from this cause. Here and there only beyond the main body of the gravel there were a few outliers, such as those at Islington and Highbury; and there habitations followed. In the same way, south of the Thames, villages and buildings were gradually extended over the valley-gravels to Peckham, Camberwell, Brixton, and Clapham; while, beyond, houses and villages rose on the gravel-capped hills of Streatham, Denmark Hill, and Norwood. It was not until the facilities were afforded for an independent water-supply by the rapid extension of the works of the great water companies, that it became practicable to establish a town population in the clay districts of Holloway, Camden Town, Regent's Park, St. John's Wood, Westbourne, and Notting Hill.

On the outskirts of London a succession of villages grew up for miles on the great beds of gravel ranging on the east to Barking, Ilford, and Romford-on the north, following the valley of the Lea to Edmonton and Hoddesdon; and on the West, up the Thames-valley to Ealing, Hounslow, Slough, Hammersmith,

Royal Commission on Water Supply, appointed April 1867. Report of the Commissioners and Minutes of Evidence and Appendix, June 1869. Poyal Commission on Coal Supply, appointed June 1866.

Reports of the Commissioners, Minutes of Evidence, Appendix, July 1871

and beyond; whereas, with the exception of Kilburn, hardly a house was to be met with a few years since between Paddington and Edgeware, or between Marylebone and Hendon; and not many even between the New Road and Highgate and Hampstead. As a marked case of the excluding effects of a large tract of impermeable strata close to a great city, I may mention the denuded London-clay district extending from a mile north of Acton, Ealing, and Hanwell, to Stanmore, Pinner and Ickenham, near Uxbridge. With the exception of Harrow (which stands on an outlier of the Bagshot Sands), and Perivale, and Greenford (on outliers of gravel), there are only the small villages of Northholt and Greenford Green. In the earlier edition of the Ordnance Maps, there was a tract of ten square miles north and westward of Harrow within which there were only four houses. Yet the ground is all cultivated and productive. But immediately eastward of this area, and ranging thence to the valley of the Lea, the ground rises higher, and most of the London-clay hills a e capped by gravel of an older age than that of the London valley, and belonging to the boulder-clay series. On these we have the old settlements of Hendon, Stanmore, Finchley, Barnet, Totteridge, Whetstone, Southgate, and others. There is yet another very common source of well-water supply from beds of gravel directing population to low sites in valleys, which is this. Everywhere on the banks of the Thames and its tributaries there is a lower-lying bed of valley-gravel or of rubble on, and often passing beneath, the level of the river. This bed is supplied with water both by rain falling on it, by springs thrown out from the adjacent hills or by the drainage from those hills and in places by infiltration from the river, when, from any cause, the line of water in the gravel falls below that of the adjacent river; while, on the other hand, the surplus landsupplies find their way direct and unseen, from the bed of gravel to the river. A great part of London south of the Thames, Westminster, Battersea, and a number of towns up the Thames, as Hammersmith, Brentford, Eton, Maidenhead, and others, together with Newbury and several villages on the Kennet, also the towns of Ware and Hertford on the Lea, have this shallow well-supply. A great many towns and numberless villages along most of our river-valleys all through England, and on whatever formation situated, are dependent on this superficial source of supply, a supply much more permanent than the other shallow well-supplies, in consequence of the outside aid from springs and rivers. It is, however, only in case of exceedingly dry seasons or of excessive pumping, that the supply requires to be supplemented by the river-waters. As, in ground of this description, the land-water is generally dammed back by the stream, the level of the water in the wells, which are always shallow, varies with the level of the water in the streams, rising and falling more or less with them.

A few of the higher London-clay hills in the neighbourhood of London are also capped by outliers of the Bagshot Sands, as, for example, Harrow, Hampstead, and Highgate, all of which are sites of old habitations. The sands at these places attain a thickness of from 30 to 80 feet, are very permeable, and afford a sufficient water-supply by means of wells to a limited population. Anumber of well-known small springs are thrown out at the contact of the sands and the clay on the slopes just below and around the summit both of Highgate and Hampstead Hills. In some instances, owing to the presence of iron in the sands, they are slightly chalybeate. When the Baghshot Sands, further westward of London, attain their fuller development of from 300 to 400 feet, the depth to the water-level at their base becomes so great that the upper porous beds are left high and dry, and form uncultivated wastes, such as Bagshot Heath, Frimley Heath, and others; but on the outside of this area, where the sands become thinner, and the water-level more within reach, we find a number of villages, such as Englefield Green, Sunninghill, Brackwell, Wokingham, Alderstone, Esher, Weybridge, Woking, &c. There are also some thin subordinate beds of clay in the middle of the series which hold up a sufficient quantity of water for small local supplies, and give rise to small streams in the valleys of the Blackwater and of Chobham. The running nature of portions of these sands, and the presence of beds of ferruginous and green sands, often interfere much with the construction of deep wells, and the quantity of the wellwater; and, externally, the mixed clay-and-sand character of the upper beds of the London clay fails to give any good retaining-line for the water, which therefore rarely issues as springs, but oozes out from the general surface of the intermediate spongy mass,

The 70 to 100 feet of sands and pebble-beds belonging to the lower tertiary strata under the London clay, and overlying the chalk, are also very permeable, and being intercalated with some beds of retentive clay, they give rise to one or two levels of water, affording wherever these strata form the surface, as at Blackheath, Bexley, Chiselhurst, and Bromley, a moderate water-supply to shallow wells. Where these sands dip under the London clay, and only present a narrow belt on the surface, a small valley is commonly formed into which the London-clay hills drain on the one side, and on the other the chalk dammed back by the Tertiary strata throws out its springs, and the sands are thus kept charged with water up to a short depth from the surface. As instances of the many places whose sites have been determined by these favourable circumstances, I may name Croydon, Beddington, Carshalton, Sutton, Cheam, Ewell, the villages between Epsom, Ashstead, and Leatherhead, to Guildford, and again between Old Basing and Kingsclere.

But besides furnishing a supply by ordinary wells to a number of villages on their line of outcrop, the Lower Tertiary sands have of late years contributed to the metropolitan supply, as well as to the supply of those adjacent districts where the surface is formed of tenacious clay, and water is scarce, by means of artesian wells. For along the line of country just named, and along a more irregular belt on the north of London, these sands pass beneath the London clay, so that the water they receive from rain and springs on the surface, passes underground, where it is prevented from rising by the impermeable superincumbent clay; consequently, as there is no outlet for the water below ground, these sand-beds are filled with water along their whole underground range, between their outcrop in Surrey and that in Hertfordshire.

I need not dwell here upon the constructions of Artesian wells, which have been explained by Hericart de Thury, Arago, Degousée and Laurent, Burnell, Hughes, myself, and others, beyond offering a few explanatory remarks on this particular case, which we shall also have to bring to bear upon the origin of springs.

The surface of the ground at the outcrop, just referred to, of the Lower Tertiary sands is about 100 ft. above the level of the Thames, whilst under London the sands are at a depth of from 100 ft. to 220 ft. below that level, thus forming the shell of a basin from 200 ft. to 300 ft. deep, the centre of which is filled with a depressed mass of impermeable clay, There is, however, a notch in the lip of the basin, where it is traversed by the Thames, at Deptford and Greenwich, which is at a lower level of 100 ft. than the rest of the rim. Below this level, as there is no escape for the water, the strata are naturally perpetually waterlogged; and if any water is withdrawn from one part, it is, owing to the permeability of the strata, at once replaced from adjacent parts of the same strata. Early in the present century, bore-holes were made through the overlying London clay to the sands at depths of from 80 ft. to 140 ft., and the water from these deep-seated springs rose at once to a height of several feet above the level of the Thames, where it tended to maintain itself, and thus form, in the lower-lying districts, permanent natural fountains. But the ease and facility with which this abundant supply was obtained, led to the construction of so great a number of such wells that a time soon came when the annual rain outfall no longer sufficed to meet the demand, or, rather, it could not be transmitted fast enough to the central area of abstraction to replace the out-draught. The consequence was that, after some years, the water ceased to overflow, and the line of water-level has gradually sunk at London, until it now stands some 70 ft. or 80 ft. beneath the surface level. This, however, is not the case at a distance from London; and in many parts of Middlesex, and more especially in Essex, where Artesian wel's are common, they have been found of very great service.

In order to supply the deficiency thus caused in the Lower Tertiary sand, most of the Artesian wells in London have of late years been carried down into the underlying chalk, which also extends beneath London at depths of from 150 ft. to 280 ft. Both formations are permeable, but in different ways. On both the rainfall is at once absorbed, but the transmission of it is effected in different ways. Through the sands it filters at once; but not so with the chalk. A cubic foot of the latter will hold two gallons of water by mere capillary attraction; but it parts with this with difficulty. Still in time it finds its way through the body of the chalk, aided by the innumer able joints, fissures, and lines of flints by which this forma tion is traversed; and, when once under the line of satura

characterises it "as an elegant and probably original contribution to the theory of the orbits of bodies moving freely in space, and acted on only by their mutual attractions."

I come now to give some account of Signor Schiaparelli's principal discovery of the law of identity of meteors and comets, and of the observations and reflections which led him to that result, as contained in a series of letters to Father Secchi in the year 1866.

It appears from these that Signor Schiaparelli's study of this subject received a great impulse from his own observation of the meteors which fell on the nights of the 9th, 10th and 11th of August, 1866. He states that he was then confirmed in the opinion expressed three years before, that, of the meteors which usually fall on those nights, a great number are distinguished by their starting nearly all from one point. And, from the spasmodic fall of these meteors-more sometimes falling in one minute than in the next quarter of an hour-he inferred that their distribution in space must be very unequal. He also observed that those stars proceeding from one point were all of a fine yellow colour, and left behind them a fugitive but very sensible track; whilst the other meteors, proceeding from various points, offered every variety of colour and form. Hence he concludes that the meteors form a number of rings, and become visible when the earth traverses their orbit, as if shooting forth from one point in the sky. And he remarks that the observa

tions of M. Coulvier-Gravier, and Professor Heis, and of our own countrymen, Professor Herschel and Mr. Greg, have shown that these radial points occur in every quarter of the heavens; therefore these rings or orbits must possess every possible degree of inclination to the ecliptic.

He then proceeds to inquire how such a mass of cosmical matter could become accumulated in the Solar System. This system seems to consist of two classes-the planets, characterised by but little eccentricity of orbit, slight variation of the plane of the orbit, exclusion of retrograde motion, and a tendency to take the form of a sphere (deviating from it only so much as is necessary to preserve the equilibrium of the body)—these characteristics applying also to the secondary systems, with the exception of the satellites of Uranus. The second class consists of cometary bodies, which are under no law as to the planes of their orbits, or the direction of their motions. The point most remarkable about them is the extreme elongation of their orbits, most of which are described in stellar space; which seems to show that they did not form part of our system when that was first constituted, but are wandering nebulæ picked up by our sun.

Signor Schiaparelli further observes that the velocity of the solar system through space has been shown by Otto Struve and Airy to be somewhat similar to that of the planets round the

sun.

Now if a nebulous body or comet in motion were to come within the action of the sun, it would go round the sun at such an immense distance from us, that it would remain invisible. Two circumstances might bring it within our range of vision first, if the comet met the sun in almost a direct line; and secondly, if it were travelling in a direction parallel to the sun's motion.

If we suppose a cloud of cosmical matter formed of particles so minute and so widely separated as to possess scarcely any mutual attraction, to be brought within the power of the sun's influence, each particle would pursue an elliptic orbit of its own. Those particles which differed most in the planes of their orbits would however possess nodes in common, and, in consequence, the particles as they approached the sun would necessarily approach each other, and when separating again, after passing the node, would at their perihelion passage be still very much nearer than they were when brought first within the sun's attraction. Those particles which, lying in the same plane, presented a wide angle with respect to the sun, would form ellipses, the planes of which would be identical; though the positions of the major axes would diverge, and, as a result, the particles at their perihelion would pass in nearly the same orbit, but at different velocities, the originally foremost particle being overtaken by those behind it. Again, those particles which, being in the same plane, were also in the same line with regard to the sun-their separation consisting in the variation of their distance from the sun-would form ellipses in the same plane, and having a major axis in the same direction, but of different lengths,-the orbit of the particle nearest the sun being described within that of the farthest particle, the result of which would be a difference of speed, and an ever-widening distribution of the particles along the whole of the orbit. This

reasoning is illustrated, in the second letter to Father Secchi, by a series of diagrams and figures; and then Signor Schiaparelli proceeds to give a recapitulation or summary of his principal propositions thus :-Celestial matter may be divided into the following classes, 1st, fixed stars; 2nd, agglomerations of small stars (resolvable nebula); 3rd, smaller bodies invisible except when approaching the sun (comets); 4th, small particles composing a cosmical cloud. This last class probably occupies a large portion of the celestial spaces, and the motion of these dust-clouds may be similar to that of the fixed stars. When attracted by the sun they are not visible unless they receive an orbit which is an elongated conic section.

Whatever may have been the original form of the cloud, it cannot penetrate far into our system without assuming the form of an elongated cylinder passing gradually into a stream of particles. The number of such streams seems to be very great. The particles are so scattered that their orbits may cross each other without interruption, and may possibly be always changing like the beds of rivers. The stream, after passing its perihelion, will be more diffuse than before; and, when passing a planet, may be so violently affected as to separate or break up, and even some particles may assume quite a new orbit and become independent meteors.

Thus meteors and other celestial phenomena of like nature, which a century ago were regarded as atmospheric phenomena -which La Place and Olbers ventured to think came from the moon, and which were afterwards raised to the dignity of being members of the planetary system-are now proved to belong to the stellar regions, and to be, in truth, falling stars. They have the same relation to comets as the asteroids have to the planets; in both cases their small size is made up by their greater number.

Lastly, we may presume that it is certain that falling stars, meteors, and aerolites, differ in size only and not in composition; therefore we may presume that they are an example of what the universe is composed of. As in them we find no elements foreign to those of the earth, we may infer the similarity of composition of all the universe—a fact already suggested by the revelations of the spectroscope.

Signor Schiaparelli further pursues the subject in another and later paper, published in No. 1629 of the Astronomische Nachrichten, entitled "Sur la Relation qui existe entre les comètes et les étoiles filantes. In this communication he refers to the letters to Father Secchi above referred to, in which he had endeavoured to bring together all the arguments in favour of the opinion of an analogy between the mysterious bodies known as shooting stars and comets.

Signor Schiaparelli, in this paper, proceeds to state that he is prepared to afford to this analogy a large amount of probability, since there is no doubt that certain comets, if not all, furnish the numerous meteors which traverse the celestial spaces. In proof of this Signor Schiaparelli quotes from a paper of Prof. Erman, in which he has pointed out the method of obtaining a complete knowledge of the orbit described by a system of shooting stars, when the apparent position of the point of radiation and the velocity through space of the meteors is known.

Assuming from the necessity of the case that the orbit of the August meteors must be an elongated conic section, Signor Schiaparelli employs the method of Erman to calculate the parabolic orbit of those bodies; taking right ascension 44° and north declination 56° for the position of the point of divergence, according to the observations made in 1863 by Prof. A. S. Herschel. And he proceeds to give the following elements, assuming the maximum of the display of 1866 to be August 10, 18 hours. Comparing these elements of the orbit of the August meteors with those of the orbit of Comet II. 1862, calculated by Dr. Oppolzer, he exhibits the following remarkable coincidence in each element :