THURSDAY, OCTOBER 19, 1893.

BRITISH BUTTERFLIES.

The Lepidoptera of the British Islands; a Descriptive Account of the Families, Genera, and Species Indigenous to Great Britain and Ireland, their Preparatory States, Habits, and Localities. Vol. I. Rhopalocera. By Charles G. Barrett, one of the Editors of the Entomologist's Monthly Magazine. (London: L. Reeve and Co., 1893.)

N°

OTWITHSTANDING the number of popular books on British insects which are constantly issuing from the press, it is only occasionally that we have to notice the appearance of a work of higher pretensions than this, even as regards our British butterflies. And yet it is of great importance that we should place on record a full and complete account of our native insects as speedily as possible. Much information that might still have been preserved fifty years ago is now irrecoverably lost, for the drainage of the fens has robbed us of many of the British insects which were absolutely peculiarto our country. But some still remain ; and notwithstanding the comparative poverty of the British insect-fauna as compared with that of the Continent, the British Islands possess a much larger number of peculiar forms than is generally imagined, and the French entomologists actually call Britain "le pays des

variétés."

The volume before us is the commencement of a comprehensive work on the whole of the British Lepidoptera (about 2000 species in round numbers) and is edited by Mr. C. G. Barrett, who is well known to entomologists as one of our best practical workers. He has had unusual facilities for personal observation in many parts of the country, and has devoted much attention to our native Lepidoptera, and more especially to some of the more difficult groups of the smaller moths; but he has hitherto only contributed to periodical literature.

The work appears in monthly parts, with plain or coloured illustrations. It commenced last year, and the first volume, including the butterflies, and illustrated with forty plates representing all the species regarded as undoubtedly British, in addition to numerous figures of larvæ and varieties, is now complete in ten parts, and has been reprinted on smaller paper, and without plates. It appears to us to be a grave oversight that there is no reference to this in the smaller edition, except in the advertisements at the end of the volume. Prominent attention should certainly have been called to the larger edition, even at the risk of injuring the sale of the smaller one, either in the preface or by a conspicuous advertisement.

In his introduction Mr. Barrett gives a concise account of the general structure and metamorphoses of Lepidoptera, and remarks on classification and synonymy. With respect to classification, everyone will agree with him in the following observations :

"Classification is, however, largely a matter of opinion. The absolute necessity-in books, lists, and collections

for a linear arrangement precludes the possibility of one which is really natural, since, although the relation of groups to each other is often evident, they ramify, extend, intersect and interlace to such a degree that it is only possible to take group after group in as natural a succession as seems to commend itself to the individual writer, with the knowledge on his part that the arrangement is partly the outcome of his own particular views, and that in all probability those of other authors are equally substantial."

But when he adds, "That which has hitherto been followed for our native species does not appear to be disturbed to a very large extent by an examination of the species found in other parts of the world," it is only so far true on account of the vast bulk of the Order having hitherto prevented any rearrangement of the families (the butterflies excepted) in a sufficiently natural series to be regarded in any other light than as tentative.

Mr. Barrett cuts the Gordian knot of synonymy, as is best in a work of limited scope, by quoting every name under which any species is widely known. No other course was open to him, unless he had worked out the synonymy of every species for himself, a work of great labour, difficulty, and at times uncertainty, or unless he had decided to follow some previous author through

out.

Dealing with British Lepidoptera only, Mr. Barrett appears to have almost confined himself to the use of English authors, from the time of Haworth, including an examination of the principal periodicals. A great deal of hitherto unpublished information is also included in the work, from the observations of the author and his correspondents. But little use appears to have been made of continental au thors, except as regards the larvæ of some of the species described.

Turning to the body of the work, we find that under each species the dimensions, essential characters, variation, larvæ, pupæ, habits, &c., are discussed in sufficient detail for most practical purposes. A useful feature of the book is the addition of many of the species which have been reputed, on fairly good authority, to have been taken in Britain, but which are still regarded either as accidental immigrants, or as doubtfully British. Of course these notices are much briefer than those of the well-established British species, about which there is no question. But we do not see what has guided the author in his selection of reputed British species; he has included such an insect as Thais rumina, a conspicuous South European butterfly, once found flying in Brighton Market, but which could hardly by any possibility be indigenous in Britain, while he makes no mention of many species recorded by the old authors as having been at least casually taken in England. As he has included such species as Thais rumina and Parnassius Delius, we think he should have given at least a passing notice of every butterfly recorded as having been taken in Britain (except, perhaps, in cases where there was reason to believe that there had been an actual error of identification, or when a careless and ill-informed author like Turton has marked species as British at random); or else have omitted all the reputed British species, except those which there was some ground for

believing might ultimately prove to be indigenous. Among the latter were many moths which were really omitted from, instead of inserted in, the British list "without authority," by the late Henry Doubleday, and which have since been proved to be indigenous, and reinstated. But we are glad to find that Mr. Barrett admits Lycana argiades and Danais Archippus among our native butterflies. The latter, though an importation from America, has been so frequently taken in England of late years, that it is hoped it may become permanently naturalised. On the other hand, there are several apparently extinct species, formerly common in England, such as Chrysophanus dispar, last taken in 1865, as well as others which appear to be now on the verge of extinction as British species, without any obvious reason, such as Aperia cratagi and Polyommatus acis. In a few years we fear that entomologists may have seriously to consider the desirability of finally erasing several of our British butterflies from our list as absolutely and undoubtedly extinct. Per contra, we may look for occasional additions (though very rarely among the butterflies) among species which are possibly overlooked or confounded with others, like Lycana argiades and Hesperia lineola, the two latest novelties. In the case of Lycana bætica, first taken in England in 1859, there is good reason to believe that the species is naturally extending its range in North-Western Europe. Possibly this may also be the case with the moth, Syntomis phegea, which is said to have been taken once or twice in England of recent years, and which, though gregarious and generally abundant wherever it is found, is excessively local north of the Alps, though there are several isolated colonies in Germany and the Netherlands.

We could have wished that Mr. Barrett had paid more attention both to the foreign literature relating to British butterflies, and to the older English literature before Haworth; but no man can accomplish everything, and within the limits to which he has confined himself his work must be regarded as by far the best and most complete which has yet appeared. W. F. KIRBY.

COOKE ON LOCOMOTIVES.

motive design. Nor is it only in the design that there is so much variation, for one finds quite as much in the systems of doing work often rigidly specified to be followed. Another point also deserves attention. Since the use of steel has come into use as a material for the construction of boiler shells, it is amusing to observe the different ways this material is handled, or rather specified to be handled. Some engineers allow the plates to be sheared to size, and the rivet holes punched full size without hesitation ; others again partly follow this practice, but require the sheared edges of plates to be planed to a depth of a quarter of an inch, and punched holes to be machined to a depth of an eighth of an inch on the diameter. Another school declines to have punched rivet holes at any price. The same variation in practice holds good with the question of annealing the plates, and particularly the flanged plates which go to form the boiler.

It is possible to take the principal parts of a locomotive and to demonstrate that what is considered good practice by one locomotive engineer is considered by some other to be decidedly wrong, and for this reason no good can be attained by following this view of the question further. Any book, therefore, treating on locomotive engineering will naturally tend to follow the practice of some particular locomotive engineer as regards design, and particularly the details, the principles of course being the same in all cases.

The volume before us "does not profess to be a scientific work; its purpose being more to give the reader, who may not feel disposed to dive into figures and cal. culations, some information about locomotives in a condensed and intelligible form." This is to be regretted, because there is no modern work on locomotive design available for reference. But on the other hand, the author has written a most readable book, useful alike to the apprentice and lay reader.

The author, being on the locomotive staff of the London and North-Western Railway, naturally follows the practice in vogue on that line, and a better example of good all-round locomotive engineering will be difficult to find.

The volume may be roughly divided into three parts ; viz. the early history of the locomotive, details of construction of recent engines, and descriptions of modern

LOCOMOTIVE engineers, like their brethren in the medical profession, very often differ widely in their practice; again, they often follow the practice of some older locomotive engineer dead and gone, may be. Who can say that the late Mr. William Stroudley has not left his mark on the locomotive design in this country, and that many British railways do not bear his handiwork in the design of their locomotive stock? To the layman the question why certain railways have engines with domes, and other railways have engines without domes, will always remain unanswered. The same may be said of bogies, injectors, pumps, &c.

In the large locomotive works, where engines are built by contract, these divergencies of practice are brought prominently forward, and one is in danger of coming to the conclusion that anything will do in the way of loco

country. In all three divisions the author has done ample

justice to the subject; although, as we have before pointed

out, the book would have been of far more value to an engineer had the author gone deeper into the question of design, and particularly the strengths of parts.

Chapter v. deals with the boiler, the most important and delicate part of a locomotive engine; for given a wellmade boiler of ample capacity, then the engine will have every chance of being a success. The author on page 91 mentions Bessemer steel as a material for boiler shells n such a way as to give an impression that it is the common practice to use that material for this purpose, whereas Siemens-Martin open hearth steel is generally used, and Bessemer steel is the exception. Further on. the tensile strength of various materials used for making boiler shells is given. Surely the author should also specify an extension or contraction of area as well?

We read that "rivet holes may be drilled, but in general practice with locomotive boilers they are punched when the plates are cold." Has the author ever seen rivet holes punched in a hot plate? It certainly is the practice to punch the rivet holes at Crewe, but no large contractor dreams of punching at all, nor would most engineers allow it to be done; and as regards cost, it is certainly no more expensive to drill.

Fig. 55 represents the arrangement for staying the crown of the fire-box by direct stays to the casing plate. This is said to be "a good arrangement." There are, however, several objections to it, the more important being that no provision is made for the expansion of copper tube plate on raising steam, the first two rows of stays being usually carried by a sling attached to the boiler shell. The old-fashioned roof-bar is again coming into vogue, owing probably to the fact that the fire-box is not held so rigidly, and therefore the plates are not so liable to crack with the constant expansion and contraction.

The chapter on boiler fittings is good, but the asbestos packed fittings made by Messrs. Dewrance and Co. might have been included with advantage. On the subject of cylinders we find much useful information, the latest types being clearly illustrated. Under the heading of general details, the radial axle-box, Adams' bogie and blast-pipe are described, but the bissel truck is not included. This is to be regretted, because it is very commonly in use abroad, and is more efficient than the radial axle-box. The all-important question of brakes is discussed in Chapter xiii. Everybody will agree with the author that it is a pity there should be two brakes in the field, because where vehicles have to run over lines using different brakes, both systems of brake gear are usually fitted: and so thoroughly has this to be done, that in the case of fish trucks used with passenger trains the cost of the brake gear comes to more than half the total cost of the vehicle.

The many improvements recently made in the design of the fittings and gear of the automatic vacuum brake have rendered it most efficient and easily maintained; a sectional drawing of the combination ejector, as made by Messrs. Gresham and Craven, would have been welcome in this chapter. The Westinghouse brake is well described, and is illustrated with the familiar sectional drawings of that company.

Chapter xiv. is on modern locomotives, and is capitally illustrated. The locomotive types on the L. and N.W.R. are described, and a table is given, being a complete list of the different standard classes with the number of engines of each class. Another table gives the numbers and names of all the passenger engines; following this chapter we find the standard types of other companies' locomotives treated in much the same manner. On p. 252 there is evidently an error. The author mentions "Mr. Stirling's 4 ft. coupled inside cylinder engines with 5 ft. 6 in. driving wheels." What does this mean? Page 266 gives the information that the Chatham and Dover Railway has the automatic vacuum as their standard brake. Surely this line is claimed by the Westinghouse Company. Scotch locomotive practice is well represented by Messrs. Holmes and Drummond's

fine engines running on the North British and Caledonian railways respectively. Page 286 contains an error in the statement that Mr. Drummond's engines of a particular type are fitted with the Bryce Douglas valve gear. One engine certainly was so fitted, but after a series of breakdowns the gear was done away with, and the ordinary link motion was adopted.

The compound locomotive is treated in Chapter xvi. Both the Webb and Worsdell types are copiously illustrated and described, but there is nothing absolutely new to be learned from a careful perusal of this chapter. No drawing is given of the Worsdell intercepting valve; but this is a mistake which can be rectified in a future edition.

The volume concludes with chapters on lubrication and packing, combustion and consumption of fuel, enginedrivers and their duties, &c. The question of metallic gland packing is just mentioned, and that is all. There are hundreds of engines now running fitted with the Jerome metallic packing, or that of the United States Company, and descriptions of these would not be out of place in this work.

Taken as a whole, this volume contains much readable and useful matter. The author has certainly succeeded

in writing a most interesting book, which is sure to leave many clear notions, on the minds of its readers, concerning the practical side of a subject of vast importance. Most of the illustrations are very clear. The printing is good, and the volume is strongly bound.

N. J. LOCK YER.

WEATHER PROPHESYING. Sécheresse 1893, ses Causes. Par l'Abbé A. Fortin, Curé de Châlette. (Paris: Vic et Amat, 1893.)

WH

JHATEVER effect such a period of drought as that through which some parts of England and the Continent have recently past may have had on the harvest, it is pretty certain to be followed with a heavy crop of literature. Some writers content themselves with a simple record of facts, and a comparison with similar experiences in the past; some try to explain the causes, and others have remedies to suggest which may diminish the ill effects of similar periods in the future.

The work quoted above belongs rather to the two last categories, but unfortunately we cannot congratulate the author on his contribution to either the scientific or the economical side of the question. His explanation of the cause of the drought is easily expressed, though we cannot hope that the suggestions put forward will carry conviction to the readers of this journal. In the opinion of the author, the drought is due to three contributory causes. (1) To the sun-spots, which for the three months in question exhibited themselves, it is stated, on the southern side of the sun. (2) To the fact that during the three months, March, April, and May, "Vénus s'est trouvée en opposition constante et prolongée." (3) The third cause is due to the fact that from the beginning of the year the lunar apogee has coincided with the new moon, and the perigee with the full moon.

M. l'Abbé Fortin has apparently many readers and admirers. If we have understood the text correctly, he

publishes an almanack in which the weather predictions are given a year in advance, and to judge from the advertisement, these predictions have met with a ready circulation. Further than this, it is mentioned with pardonable pride, that when the gifted author was in need of a micrometer for the prosecution of his studies of these sun-spots, a generous and a sympathising public subscribed 700

francs with a readiness and devotion that should attest the usefulness of his labours and his popularity. With these advantages on his side we feel the responsibility of venturing to disagree with him, or of questioning his figures and his results. Nor is any hope entertained of convincing him of the inadequacy of his arguments, and some apology is perhaps due for pointing out one or two facts which, if they do not convict the reverend Abbé of misrepresentation, exhibit at least a want of candour, which we should not have expected to meet in one of his sacred calling. We may pass over his first argument resting on sun-spots, because it is not impossible but that these do exercise an influence on our atmosphere not yet explained, though we are certain that the warmest adherent of such a theory will find little additional supfrom the arguments stated by the Abbé. It may not port be possible to do justice by a translation to the words "opposition constante et prolongée," as applied to Venus. By" opposition" is evidently meant superior conjunction, but why constant and prolonged? The superior conjunction of Venus did not take place till the beginning of May, and we regret to say that the words "coincident cette année 1893 avec les mois de Mars et Avril" (p. 46) are. unwarranted and misleading. The same remark applies to the words (p. 90), “ Vénus ne se rapprochait de sa conjonction qu' en Juillet," and it may further be remarked that since Venus was approximately at the same distance from the earth in the beginning of July as at the beginning of March, June ought to have been included in this "constant and prolonged opposition." Again, with regard to the moon's apse, it is declared (p. 90), “il arrivait encore que l'apogée se faisait juste en pleine lune, et le perigée à la nouvelle lune." A comparison of the dates of new and full moon with those of perigee and apogee shows that the Abbé is not more accurate here than in his remarks on Venus. The average deviation for the three months under notice is two and a half days, and in one case the time of full moon was March 31, 19h, while the apogee did not occur till April 5, 7h., or a difference of time of four and a half days. But the curious and to some extent the most interesting feature of the whole is, that the admirers of the Curé will still continue to regard him as an authority, and, what is more to the purpose, eagerly purchase his almanacks, and would continue to do so even if his errors were more palpable-more numerous they could scarcely be.

The remedy which the gifted author would apply to prevent a recurrence of the ill effects which have made themselves felt this year consists in an extensive system of irrigation. Doubtless financial considerations would enter in a perplexing manner into such a scheme, and prevent it becoming a part of practical agriculture. But the knowledge of local circumstances which the Abbé probably possesses, and certainly we do not, permits him to speak with an authority we do not like to question.

W. E. P.

OUR BOOK SHELF.

Geological and Solar Climates: their Causes and Varitions. A Thesis. By Marsden Manson. (London: Dulau and Co., 1893)

SEVERAL thinkers have from time to time set to work te enlighten their fellow-creatures on the subject of the cause both the temperate and the tropical areas. Each one has of the Ice age, a period when ice covered quite generally in his own way added something towards the solution of this problem, whether that something was large or small, but the theory that will produce conviction in all minds, or rather in the majority of minds, has yet to come. The causes which have been suggested are many and varied. Some say the age was due to a decrease in the original heating of the globe; changes in the elevation of the land, and therefore varied land and water distributions; changes in the position of the axis of the earth; while others account for the phenomenon by suggesting a period of greater moisture in the atmosphere; variations in the amount of heat radiated by our sun; variations in the absorbing power of the sun's atmosphere; variations in the temperature of space; coincidence of an Aphelion winter with a period of maximum eccentricity of the earth's orbit; a combination of the last mentioned with that of changes in the elevation of the land; and lastly, the explanation recently put forward by Sir Rober: Ball.

In the present thesis the author, after reviewing briefly the suggested explanations, goes back to the idea of the decrease in the original heating of the globe, and on that builds up a very plausible theory. To state briefly this theory, one must mention that two sources of heat were earth, and second that of the sun. As the earth passed at work-first that of the resident or internal heat of the from the era in which its climates had been controlled by internal heat to one in which solar heat predominated, uniform climates "must have been passed through during which isotherms were independent of latitude." Before the era was reached at which the sun had complete control over the climates, the author says the continental areas must have been glaciated, independent also of latitude.

To state in so many words the direct cause of the Ice age, he says that it is due to the remarkable properties of various forms of water in relation to heat and cold. As vapour it played an enormous part in the loss and receipt of heat by radiation, as water it was the last to retain "the effective remnant of earth heat, on account of its high specific heat, and as ice it was able to store a great amount of cold."

The author then deals in detail with the way these three forms of water played their part in this stupendous phenomenon.

The end of the Ice age was brought about so soon as the solar heat could find its way to the earth's surface: the air being cleared of obscuring clouds and fogs by the chilling of the oceans and the glaciation of continental

areas.

The first zone over which the solar energy would first establish its power would be the torrid zone; travelling polewards the glacial conditions would gradually be removed upon lines parallel with the present isotherms.

More on the subject need not be said here, but we would recommend any one who takes an interest in this problem to give this book a perusal, for although there may be many who would not agree with the writer in all points, yet he has made an honest and plausible attempt at suggesting a cause of one of the most difficult and yet most fascinating problems with which we have to deal. A Manual of Electrical Science. By George J. Burch. (London: Methuen and Co., 1893.)

Of the many useful volumes in the University Extension Series published by Messrs. Methuen, this is one of the

best. "I have written," says the author, "not for wealthy amateurs, nor for people who do not care to think, but for men and women who have to give up something else to spend a sovereign on their own education. Nearly all the apparatus described in this book can be made by anyone with a few tools and a little finger-skill." In conformity with this laudable desire, technical terms are rarely introduced without being explained, and by simple words and apt illustration the way to electrical knowledge is made as easy and pleasant as it possibly could be. Indeed, popularity of style appears to be the book's sole raison d'être, for, with one or two exceptions, the facts described are to be found in a number of elementary text-books. However, it can be said that there are very few, if any, books of the modest dimensions of the one before us in which so much information is imparted in a more popular manner. The descriptions of experiments and principles are easy reading without being diffuse; the hydrostatic and other analogues are numerous, yet they are never used where likely to lead to a misconception. The illustrations, however, are not worthy of the text. They should have been far more numerous and less sketchy in order to appeal to the public for whom the book has been specially designed.

LETTERS TO THE EDITOR. [The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE. No notice is taken of anonymous communications.]

The Supposed Glaciation of Brazil.

IN the second volume of NATURE, p. 510, I reviewed the late Prof. Hartt's "Geology and Physical Geography of Brazil," and called attention to the author's views, as well as those of the late Prof. Agassiz, relating to the supposed glaciation of that country. From their very positive statements I concluded that the evidence as described by them did actually exist, and that until it was disproved it should not be ignored. In my 'Darwinism," p. 370, I stated, on the authority of my friend, Mr. J. C. Branner, now Professor of Geology in the Stanford University, California, who succeeded Prof. Hartt in Brazil, and had a much more extensive knowledge of the country, that the supposed glacial drift and erratic blocks were all results of subaerial denudation. Recently, however, Sir Henry Howorth has quoted some passages from my review in illustration of the wild and incredible theories of some geologists, as samples, in fact, of the "Glacial Nightmare"; and, as no authoritative disproof has yet been given of the exceedingly strong and positive statements of Agassiz and Hartt, I beg leave to lay before the readers of NATURE some extracts from a paper on "The Supposed Glaciation of Brazil," by Prof. Branner, which will shortly be published, and of which he has kindly sent me a type-written copy in advance. As a partial justification of what has now proved my too hasty acceptance of the statements of these gentlemen, I will give one passage in which Prof. Agassiz refers to the supposed glacial phenomena near Ceara :-"I may say that in the whole valley of Hasli there are no accumulations of morainic materials more characteristic than those I have found here, not even about the Kirchel; neither are there any remains of the kind more striking about the valleys of Mount Desert in Maine, where the glacial phenomena are so remarkable; nor in the valleys of Loch Fine, Loch Awe, and Loch Long, in Scotland, where the traces of ancient glaciers are so distinct." Both Agassiz and Hartt were equally strong as to similar phenomena near Rio.

It is to be first noted that Hartt had only spent eighteen months in Brazil when he wrote his book, and his views on the glacial phenomena were thus based on a very hasty survey of that enormous territory. Prof. Branner went with him when he again visited Brazil in 1874, helped him in his geological work till his death in 1877, and himself remained five years longer making a geological survey of the country; and he states that, before his death, Hartt's views underwent a radical change. Prof. Branner says:

"Under his direction I did more or less work in the moun. tains about Rio de Janeiro for the purpose of sifting the evidence of glaciation in that region, and I am glad to say, in justice to the memory and scientific spirit of my former chief and friend, that long before his death he had entirely abandoned the theory of the glaciation of Brazil, and that the subject had ceased to receive further attention, even as a working hypothesis."

A few extracts must now be given showing to what causes the phenomena which deceived these observers are really due. And first as to what were supposed to be erratic boulders often embedded in boulder clay.

"The boulders believed to be erratics are not erratics in the sense implied, though they are not always in place. The first and most common are boulders of decomposition, either rounded or subangular, left by the decay of granite or gneiss. Sometimes they are embedded in residuary, and therefore unstratified, clays, formed by the decomposition in place of the surrounding rock. And everyone has heard of the great depth to which rocks are decomposed in Brazil. The true origin of these boulders and their accompanying clays is often obscured by the 'creep' of the materials, or in hilly districts by land slides, great or small, that throw the whole mass into a confusion closely resembling that so common in the true glacier boulder clays. In this connection too much stress cannot be placed upon the matter of land slides; they are very common in the hilly portions of Brazil, and aside from profound striations and facetting produce phenomena that, on a small scale, resemble glacial till in a very striking degree."

"The second method by which these boulders have been formed is quite similar to the first, but instead of being cores of granite or gneiss, they have been derived by the same process of exfoliation and decomposition from the angular blocks into which the dikes of diorite, diabase, or other darkcoloured rocks break up. Their colour marks them as quite different from the surrounding granites, and the dikes themselves are almost invariably concealed. The residuary clays derived from the decomposition of these dikes are somewhat different in colour from those yielded by the granites, so that when 'creep' or land-slides add their confusion to the original relations of the rocks the resemblance to true glacial boulder clays is pretty strong. The chance of discovering the source of such boulders is further decreased by the depth to which the mass of the rock has decayed, and by the inpenetrable jungles that cover the whole country, and so effectually limit the range of one's observations. Dikes, such as these last mentioned, are not uncommon in the mountains about Rio de Janeiro. Indeed, what have generally been regarded as the very best evidences of Brazilian glaciation, some of the boulders near the English hotel at Tijca, fall under this head, though some are of gneiss. The fact is that the great mountain masses about Rio are of granite or gneiss, while some of the boulders come from the dikes of diabase or other dark-coloured rock high on their sides-dikes which were not visited by Agassiz or Hartt."

Prof. Branner then describes a third class of supposed erratic, derived from certain sandstone beds of the tertiary deposits, which, by exposure, change to the hardest kind of quartzite, and when the surrounding strata are removed by denudation, and a few blocks of this quartzite are left, they are so unlike the rocks by which they are surrounded that unless the observer has given a special study to the tertiary sediments, he is liable to be misled by them.

The wide-spread coating of drift-like materials tha covers considerable areas of the country, consisting of boulders, cobbles, and gravels, sometimes assorted and sometimes having clay and sand mixed with them, are then described, and are shown to be due to the denudation of the tertiary beds during the last emergence of the land, aided by subsequent subaërial denudation and surface wash. Prof. Branner thus concludes :"I may sum up my own views with the statement that I did not see, during eight years of travel and geological observations that extended from the Amazon valley and the coast through the highlands of Brazil and to the head waters of the Paraguay and the Tapagos, a single phenomenon in the way of boulders, gravels, clays, soils, surfaces, or topography, that required to be referred to glaciation."

The very clear statement above given of the real nature of the phenomena which deceived Prof. Agassiz and Mr. Hartt, is very instructive, and it shows us that a superficial resemblance to drift, boulder-clay, and erratic blocks, in a comparatively unknown country, must not be held to be proofs of glaciation.