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insisted on, it would, of course, be absurd to attempt to THURSDAY, APRIL 20, 1893.

compel the governing bodies of existing institutions to surrender all their rights off hand, or to treat as hostile

men who have been doing their best for the public good THE NEW UNIVERSITY FOR LONDON.

amid great difficulties and with too little public sympathy.

We cannot, therefore, but hope that the Commission THE long procession of witnesses which for months may recommend, and the Colleges accept, some such

past has been defiling before the “Gresham Univer- plan as that recently proposed by the Professorial sity Commission " has at length come to an end. The | Association. Commissioners are now, we suppose, engaged in con- In this scheme a praiseworthy attempt has been made structing a scheme for the constitution of the University. to combine a rigid insistance on the conditions necessary Their manner of performing the first portion of their task for the future success of the University, with a due regard has been open to criticism. More may be heard here for the susceptibilities of the Colleges out of which it after of the extraordinary refusal to furnish the witnesses will in part be constituted. It is proposed that the with copies of their own evidence, and of the still Governing Body shall consist of the Chancellor and more remarkable fact that, though the majority were the Vice-Chancellor, and twenty-five Professors (each of denied copies of what they themselves had said, excep- whom shall be elected annually by the Professors of a tions were made in the case of certain favoured persons definite group of cognate subjects), together with fourteen who were allowed to see and to contradict the evidence members nominated by the Crown, four members nomiof others.

nated by its Corporation and the London County While the Commission has been sitting several Council, three representatives of Convocation, and four schemes for the constitution of the new University have members, not being teachers in the University, nomibeen proposed. In spite of certain important differences nated by the Governing Body itself. there is one most important point on which they are the last provision would enable the Court-as the generally in accord. It is not too much to say that Governing Body is called-to give temporary or permanent with no more exceptions than are necessary to prove the representation to public or semi-public bodies which it rule-every one interested in the future development of might be desirable to attach to the University. It is also the higher education in London agrees that there should proposed that the arrangements between the University be but one university in the metropolis, and that it should and the existing colleges shall be negociated by a not (as was proposed in the discredited Gresham scheme) Statutory Commission with very wide powers, subject be a loose federation of competing colleges. It cannot always to the condition that every Professor of the be too strongly urged that the object of a university is the

University, wherever he may teach, shall be appointed promotion and the diffusion of learning, not the ag- and paid by the University. To this Commission is en. grandisement of educational institutions. Every student trusted the task of selecting in the first instance the in London who can pass the prescribed examinations fourteen members of the Court, whose successors will be can at present obtain a degree. No change in existing nominated by the Crown. The choice is to be made arrangements need be made unless it can be shown by “from among the existing members of the Senate of the some other method students could be attracted in greater University of London, and from members of the numbers, or could be turned out at the end of their governing bodies of those colleges which may be incoruniversity careers with a greater mastery of the branches porated, in such proportion as may seem advisable to the of knowledge which they have studied. These ends will Commission, having regard to the importance of the not be attained by giving to the existing colleges the vested interests involved, and to the magnitude of the right to agree among themselves as to the conditions on educational resources which may be placed by each at which degrees are to be bestowed, and leaving the existing the disposal of the new University. These initial apuniversity as a rival whom they will immediately be pointments are to last for ten years, and at the end of ten tempted to undersell. If public money were bestowed on years, or in the event of vacancy through death or such a university it would merely be scrambled for by resignation, the appointments are to be made by the the constituent colleges, and would be spent in a rivalry Crown." Subject to the general control of the Court the in which the minimum advantage to learning would be Professors of the University are to have charge of all produced by the maximum waste of funds.

purely educational matters. If London is to have a University worthy of the name, i The colleges named as those which it is desirable if Parliament, the City Companies, and the London to bring into connection with the University are (in County Council are to provide it with the means abso- alphabetical order) Bedford College, the Central Instilutely necessary for its proper equipment, the University ; tution of the City and Guilds Institute, Gresham College, must be endowed with powers which will enable it to King's College, the Medical Schools, the Royal College fashion the Colleges to meet the needs of London. It of Science, and University College, while there are other must be freed from, not fettered and hampered by, the institutions, especially those giving instruction in Fine necessity of maintaining in precisely their present Arts and in Law, with which it may be possible for the form arrangements which are themselves in large University to establish relations. It is also proposed measure the result of the religious animosities of fifty that the University should have the power to appoint or years ago.

to recognise teachers giving instruction of a more or less But while this fundamental fact must in every way be academic character at institutions or colleges, the objects or the standing of which render complete incorporation of the book is made, however, it is impossible not to be with the University undesirable, and to institute struck with a certain inequality of treatment on the pa “ University Extension” lectures, always, however, sub of the editor : and as we sincerely hope this excelles ject to the condition that the teaching functions of the book may reach a second edition, it may be well to a University are to be confined to the metropolitan area. attention to points in which it is certainly susceptible The examinations of the existing University of London improvement. would of course be carried on, so that in this part of its There are two ways in which a teacher of geology work the University would maintain its connection with any particular country may advantageously introduce all parts of the kingdom, and indeed of the empire.

students to the comparative study of the several forma In all these points the suggestions of the Association tions. He may, in the first instance, describe the for appear to us to be eminently practical. It is hopeless to mation as displayed in an area where his students can make expect a solution of the problem to which every one will direct acquaintance with it, and then proceed to poin agree. The first desideratum is to secure the establish: out the resemblances and differences presented by the ment of a new non-federal teaching University, and then | various foreign equivalents of the formation; and therei to give a statutory commission the power to make bar

the power to make bar- | certainly much to be said in favour of thus making geologi gains with the existing colleges, which must either assent “ begin at home." But, inasmuch as the several system to reasonable terms or be left outside the University of strata are very unequally developed in different areas altogether. If any Governing Body consents to a close there is often a very obvious advantage in following: incorporation with the University it will secure repre

different plan. If the district in which the most sentation on the Court both from among its lay members perfect exhibition of a system of strata can be studiel and its Professors. When the University is fairly started be selected as the type, and all other areas be direc. the Crown will select persons who are or are not connected compared with this typical representation of the system with the Colleges as may seem desirable. The Medical | it is evident that a more satisfactory account of a forma Schools will be free to make terms with the Statutory | tion can thus be given in a limited space than is possiba Commission or to remain independent as they please. by the other method. Of course the Commission ought to be as strong as pos

Now as regards the Palæozoic formations, we thal sible, and much will depend on it, but with the suggested that Mr. Lake has been very happy in the methods by constitution it would be impossible to make the University has adopted. In the case of the Cambrian, Ordovician a federation. It would be independent of and superior

Silurian, and Carboniferous systems, he has cominence to the Colleges. It would be powerful and important with an account of their development in the Britis enough to bulk large even in London, and to attract

Islands. The Devonian and Permian are, however help both from the State and the Municipality.

differently dealt with, the type of the first being sough in the Eifel and of the second in Central German Nothing could be better for the purpose aimed at tha

this blending of the two different methods of treatmen COMPARATIVE GEOLOGY.

to which we have referred.

In his preface the author acknowledges the assistand Text Book of Comparative Geology. By E. Kayser,

received from Mr. Marr and Prof. Lebour in prepara Ph.D., Professor of Geology in the University of Mar

the account of the Palæozoic rocks; and every one m3 burg. Translated and edited by Philip Lake, M.A.,

be satisfied with the general accuracy and fulness of trea! F.G.S., late Harkness Scholar in the University of

ment of the British strata and their equivalents, so far a Cambridge. With 596 Illustrations (73 plates and 70

the great Palæozoic systems are concerned. figures in the text). (London : Swan Sonnenschein.

The most serious criticism which we have to ofier wi New York : Macmillan and Co., 1893.)

respect to this earlier portion of the work is as regard AMONG works dealing with stratigraphical or his- the limits adopte d for the Cambrian. Mr. Lake divide

1 torical geology, Dr. E. Kayser's “Lehrbuch der this system into three portions, characterised by the geologischen Formationskunde” holds a deservedly high Olenellus, the Paradorides, and the Olenus fauna re place. The account given in this work of the several spectively; he nevertheless takes away from the Cambs. geological systems, as displayed in Germany, is very full the Tremadoc beds, in which Olenus is so abundant, ani and complete ; and the comparisons of the German strata | makes them the base of the Ordovician. We think that with their equivalents in other parts of Europe are for in a work intended for English students, it would hav the most part judicious and accurate. A very striking been better to have followed the practice which ha and admirable feature of the book is its wealth of illus- hitherto prevailed in this country, and to have include tration; carefully selected specimens of the character the Tremadoc in the Cambrian, giving a reference to 1 istic fossils of the several formations, are figured in such Kayser's views in a footnote. a way as to be clearly recognisable, and there is probably We also find in the preface an admission that “addi no text-book of the kind in which the number of forms tions are most numerous in the first half of the work thus represented is anything like so great.

while in the latter half the greatness of the subject 2r1 We cannot but think that Mr. Lake has rendered a the limits of space have made themselves more severe! great service to geological students in this country by felt." In the account of the Jurassic and Cretacetei translating Dr. Kayser's admirable text-book; and for the strata there are not a few important facts with respect : 1 general manner in which he has performed his task we the British representatives of those systems that at have nothing but praise. When a detailed examination altogether omitted ; while there is, we think, a dispropas ionate amount of space given to some foreign equivalents. Although we have felt it to be our duty to call attention tis when we come to the Tertiary strata, however, that to certain imperfections and blemishes in this book, we

e are most painfully impressed by the inadequacy of the must repeat our verdict concerning its general excellence, reatment of some very essential matters. The British and the hope that an opportunity will soon be afforded Docenes have about half a page devoted to them ; there to its editor of preparing a second edition, in which these 5 no mnention of the Hampshire Basin as distinct from imperfections and blemishes may be removed. bat of London ; and the table of strata given is neither hat of one basin nor the other, but an awkward combinaion of beds from both. The English Oligocene is dis.

THE BALTIC SHIP-CANAL. nissed in about a dozen lines, and no mention is made of he rich and varied marine fauna of the New Forest.

Der Nord-Ostsee-Kanal. Von C. Beseke. (Kiel and About the same amount of space is devoted to the Pliocene

Leipsic: Lipsius and Tischer, 1893.) f East Anglia (that of the South Downs and Cornwall | FOREMOST among the engineering works of the tot being even mentioned), while the highly developed i

latter part of the nineteenth century must assuredly Pliocene of Belgium has assigned to it only a single line.

be placed the magnificent maritime canals, which afford We make these remarks, not with any desire to find such conspicuous evidence of industrial skill and enterault, but in order to call the author's attention to the prise ; and of these great works few will yield in point of act that, in its present state, the work would be alınost size and importance to the new sea-way between the North useless to an English student, unless he used it in con

Sea and the Baltic, the history and progress of which junction with another geological text-book, in which the ' is so ably described by Herr Beseke in the present British formations had received more adequate treatment. ! volume. If the more vigorous editing, which has made the first The idea of such a canal has been under consideration part of this book so excellent, were applied to the latter' for five centuries, and one of the most interesting chapters half of the volume, we should then have an almost perfect in the book is that which enumerates no less than sixteen work, and one which would find a place in every scientific schemes which have from time to time been propounded library.

for the accomplishment of this difficult problem. These With all its faults, however, we have a text-book of different projects are rendered all the more intelligible stratigraphical geology which is superior to all its prede-' by means of a sketch-map, indicating the various lines cessors in respect to its illustrations, and its thorough- proposed, the majority of which, having their origin in ness. The copious index is of the greatest value, though the estuary of the Elbe, passed transversely across the the work would be improved by some additions to the Schleswig-Holstein peninsula to points in the vicinity of references and the substitution in all cases of citations Kiel or Lübeck. of original inemoirs in the place of works giving infor! The inception of the present undertaking dates from mation at second hand.

October 19, 1883, when the Chancellor of State was The plan of treatment of the several geological systems' directed by Imperial rescript to report upon the execution is excellent. The historical account of the establishment of a canal from Kiel to the mouth of the Elbe. The plans, of the particular division and grouping of the strata is prepared in conformity with this decree, were adopted, followed by sketches of the development of the system in with trifling modifications, on March 16, 1886, the the chief European areas, concluding in certain cases with execution of the works being entrusted to a State Com shorter notices of some of the extra-European equivalents. mission in July of the same year, and the first stone was This account of the stratigraphy of the system is followed laid by the Emperor William I. with an imposing cereby an admirable sketch of its palæontology.

| mony on June 3, 1887. There are two portions of the book which, to make the The total length of the projected canal is about 61 work suitable as a manual for English students, require English miles, the width at the water-line is 197 feet, and to be greatly modified, if not altogether rewritten. These at the bottom, at the toe of the slopes, 72 feet; the total are the chapters relating to the Archæan and the depth is nearly 28 feet. It is shown by means of a diagram “ Diluvium " respectively. We can readily understand that not only will two of the largest Baltic merchant that the editor would shrink from so drastic a remedy as vessels pass one another without difficulty, but also that we suggest, and yet the views expressed in the book before there is room for a vessel of this type to give way to one us, upon the oldest and youngest of the formations re- of the finest ironclads of the German navy, such as the spectively, are so entirely at variance with those which the König Wilhelm, with a displacement of 9757 ton s. beginner is likely to hear from any recognised teacher of Special passing stations have, however, also been argeology in this country, that it is scarcely fair to students ranged at intervals, similar to those on the Suez Canal. to allow them to stand in their present form. In the same The cost of the works was originally estimated at way the uncompromising statements concerning the £7,800,000, which provides for 77,400,000 cubic metres difference between the eruptive rocks associated with the of excavation, and all requisite contractors' plant and tertiary and those of older geological epochs require materials, entrance locks, bridges, and harbour works, as serious qualification. If the editor felt that he could not, also for the forts needed to protect the western approach in fairness to the original author, make the necessary to the canal. omissions or alterations in the text, he might have ap- ' A most curious chapter is that which deals with the pended potes in which the attention of the student is called provision made for the conduct of the enterprise, and for 10 statements that are at variance with the instruction he the housing and accommodation of the large staff of would ordinarily receive in this country.

I workpeople engaged therein. The sub-contractors for

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the various sections into which the works were divided John Lubbock. It is concerned with the meaning of the 15 in number-had, under conditions carefully specified, terms applied to matter, and with the principal properties to construct barracks for the staff of workers. The can.

which matter possesses, and contains chapters upon units teen arrangements were all carefully thought out, and the

of measurement, force and motion, work and energy, tre

forirs of matter and of energy, and upon the properties et prices of food were regulated by fixed tariffs. The sizes

solids, liquids, and gases. of dormitories were prescribed ; hospitals and laundries The book is an excellent introduction 10 the study of have to be provided, and all the sanitary arrangements the physical properties of substances, and meets the main appear to be most complete.

difficulty of the beginner by supplying him with sound It was a condition of their engagement that the work

ideas on the ground-work of his subject. It is indeed a

matter for regret that there are so few similar books or people should be at least seventeen years of age, no

other branches of science. Socialists or Anarchists might be employed, and all

Although the properties discussed are almost entire drunken and dissolute persons were liable to instant dis mechanical or physical, the author occasionally touches missal. Some of the regulations appear slightly auto upon the subject matter of chemistry, and here the cratic, but doubtless with a population of from 6000 to

chemical reader may perhaps be puzzled to find the term 8000 persons brought together from all parts of Germany,

“molecule" applied in cases where he has been taught to

use the term “atom." The molecular weights given om such as was to be found on certain of the sections, it was

p. 184, for example, are the ordinary atomic weights of necessary to insist upon a very severe discipline. We the chemist. It is impossible, however, to correctly ds. are assured by the author that hitherto these rules have cuss even such chemical phenomena as are given in the worked satisfactorily. A detailed account is given of the book, without employing the conception of atom as well four bridges required for the railway crossings, also of the

as that of molecule. Thus on p. 183 it is stated that be numerous ferries and of the massive constructions needed

adding to each molecule of carbonic oxide a second

molecule of oxygen we get carbonic acid." This coc to form the entrance-locks of the canal at either end.

clusion is not in harmony with Avogadro's hypothesis, kur The water-level of the canal is almost coincident with carbonic oxide unites with half its volume of oxygen :3 that of the Baltic. So that on 340 days in the year the form carbonic acid. sluices can remain open, and the lock-gates into the Elbe The value 411° is much higher than those recently can be opened daily at certain states of the tide ; the water

obtained for the critical temperature of water. On pid

“dynes in a given mass” should be “dynes in a give? in the canal is to be at one uniform level throughout

weight." The formulæ on pp. 164 and 180 are not com In consequence of the advanced state of the works it

rectly printed.

J. W. R seems probable that the undertaking may be formally opened for traffic at the period originally contemplated, in

The Partition of Africa. By J. Scott Keltie. (London the summer of 1895. Steamers will be permitted to Edward Stanford, 1893.) propel themselves at a mean speed of about six miles an

The author of this book does not wish it to be regante i hour, and sailing vessels and barges will be towed in train

as a contribution either to the geography of Africa or try through the canal by steam-tugs provided for this purpose. the history of African exploration. His object has bee

Herr Beseke presents us with most exhaustive statistics to present “ a brief connected narrative of the remarkable showing the saving in time caused by the use of the canal

events which, during the last eight years, have led to the as contrasted with the dangerous passage round the coast

partition of the bulk of Africa among certain of the powers

of Europe.” In carrying out this purpose, Mr. Kelle of Denmark, and a wreck chart of the entrance of the

displays wide knowledge, sound judgment, and an adBaltic serves as an effective object-lesson of the value to

mirable power of lucid and effective exposition. Thel navigation of this new sea-way.

details of his narrative do not come within the scope o In the concluding chapters we find most ample details NATURE, but we may note that in his occasional reference of the volume of Baltic commerce and of the tonnage en

to the scientific aspects of the subject he invariably gives gaged therein, both in the form of steamers and sailing

evidence of a thorough grasp of the principles which can

alone be of vital service in the study of geography. This vessels, and excellent diagrams and charts have been

is especially true of a luminous and interesting chapter om specially prepared by the author to render these facts

“the economic value of Africa." The importance of the readily intelligible to the public. Nor does Herr Beseke work is greatly increased by a large number of caref:", omit to treat of the industrial value of these works and of selected and well-executed maps. their importance to the Fatherland, both from the military and naval aspects ; in fact their political significance is

Forest Tithes, and other Studies from Nature. Byd shown to be enormous.

Son of the Marshes. Edited by J. A. Owen. (London The volume contains a mass of well-digested informa

Smith, Elder, and Co., 1893.) tion upon an undertaking concerning which but little has

By “forest tithes” are meant the quantities of food hitherto been heird in this country, but which is destined

secured at the expense of rural folk by wild creatures a

the moorlands. The subject is an attractive one, and :* to exert a powerful influence upon the commerce of the

dealing with it the author of this little volume pre states bordering upon the Baltic.

sents many bright and lively sketches of animal life

The essays on other subjects are in their own way res OUR BOOK SHELF.

less pleasant. They all display an ardent love of nature

and a remarkable power of minute and accurate observa Laws and Properties of Matter. By R. T. Glazebrook,

tion-qualities which have won for “a Son of the M.A., F.R.S. (London : Kegan Paul, Trench, Trübner Marshes" a place of his own among the popular writer and Co., 1893.)

of the day. Some of the articles have already appear to This is the latest addition to the manuals on “Modern in various publications ; others are now printed for i** Science " which are appearing under the direction of Sir first time.

LETTERS TO THE EDITOR.

any doubt that the new factor in this case was the excessive rain

fall of last February, and the want of sufficient under-draining The Editor does not hold himself responsible for opinions ex: to carry away the water, which entered the mass of partly-com

pressed by his correspondents. Neither can he undertake pacied débris from above. A small lateral valley parallel with to return, or to correspond with the writers of, rejected the general line of the escarpment had no doubt served as a manuscripts intended for this or any other part of NATURE. catchment agent for much of this water. This supposition is No notice is taken of anonymous communications.]

borne out by the facts (1) that further to the east, where a land. Locusts at Great Elevations.

drain was laid some years ago, the mass below it remained stable ;

(2) that above the western end of the slip" the military hosTHE following account of the occurrence of swarms of locustspital suffered no damage, the stability of its base being doubtless at great elevations in the Himalaya, and these stripping birch due to the complete under-draining of the site, which, as my trees, is from a privately printed record of an expedition to the kind friend and host Colonel Cranmer Byng informed me, was north-east of Kinchinjunga, in 1891, by Ms. White, the British carried out before the hospital was built. It is probable, how. resident in Sikkim. That flights of locusts are carried from ever, that at the point of inaximum movement the springs from the plains of India up to great heights in the Himalaya is a the beds which form the plateau above had much to do with well-known fact ; but not, I think, in the numbers oor with the the water-logging and consequent diminution of the internal results to birch or other forest trees here recorded.

friction of the débris which moved, and that the action of those The Camp, April.

J. D. HOOKER. springs was exceptional or excessive in the early part of this year, "On July 19, 1891, I crossed the Lunglala Pass, 17,400 feet

owing to the rise of the water-line in the ground at the back of .... On the Pass I saw the locusts that had insested

the escarpment. Darjeeling, for the first time, though subsequently I saw them

I have talked the matter over with Mr. Topley, who is an as high as 18,000 feet, where they were dying in the snow. It

expert on all matters of Wealden stratigraphy, and he agrees will be remembered that this was the year of the great plague

generally with me as to the real nature of the phenomenon. of locusts in Malie. I heard that they had penetrated even into |

There is one obvious and only preventive against its recurrence. Tibet. On the 21st I came down as far as Tangu, 12,750 feet,

Wellington College, Berks, April 15.

A. IRVING, where the locusts were in swarm and dying in thousands. The only plants they seemed to care about were the birches, and these they stripped bare."

“Roche's Limit."

I MUST thank your correspondent G. R. for correcting my The Sandgate Landslip.

carele:sness in giving Roche's limit round the sun as about a As I have just returned from Folkestone, and have had oppor

tenth of the earth's distance, instead of about a ninetieth as it tunities for observing the recent" landslip" at Sandgate, perhaps

really is. a note on it may be of some interest to readers of NATURE, as I

IMR is the radius and D the density of a spherical planet, and do not think the explanation suggested by Mr. Blake in Nature

d the density of the tidally disturhed and infinitesimal satellite, (vol. xlvii. p. 467) is altogether applicable to the present

moving in a circular orbit so as always to present the same face instance.

to the planet, then ihe distance at which the satellite is on the So far as I could see from a careful examination of the ex

point of being broken up by the tidal forces is 2.44 R R (D/d). 1 posures, there is no trace of any movement of the solid rocks

This is Roche's limit, and the formula is correctly stated by of the cliff, as these are nowhere exposed in the fissures that

G. R. have been formed by the earth movements; and my impression! The mean density of Jupiter is about one third greater than from all that I saw is that the "slip” has been entirely confined | that of water, and it does not seem unreasonable to suppose that to the débris which has accumulated in past ages against the the density of the fifth satellite may be as low as 2. This would Aank of the escarpment. On referring to the four types of bring the limit to 2'13 R. Bergstürze or landslips described by Prof. A. Heim, of Zurich. Any plausible hypothesis as to the density of the stones formsome years ago in a monograph, which was summarised (with ing Saturn's rings will no doubt bring the limit somewhat inside additions) by myself in the Geological Magasine (Decade II., vol. x. p. 160 et seq.), it is not difficult to identify the Sandgate I must plead guilty to not having made these numerical incident with the first class of such phenomena, to which Prof.

estimates whilst writing my review of Mr. See's paper. How. Heim gives the name “ Schuttrutschung"; that is to say, a

| ever, it suill seems to me that the coincidences which I there slide or push of an accumulation of débris (Schuit). Such ac

nvied are very remarkable. cumulations often in mountain regions occur as lateral moraines

The simple illustration by which G. R. obtains a fair approxi. or as talus ; and in my paper on the origin of valley lakes / mation to Roche's limit is very interesting. (Quir. Jour. Geol. Soc., vol. xxxix., February, 1883) I have The satellite is replaced by two small spheres of density d and altempled to show how such masses play an important part in

radius r, touching one another, in line with the large sphere of the formation of some lakes. The Sandgate phenomenon I

density D and radius R. Suppose that when the point of contact lake to be no more than a magnified instance of what

is distant c from the centre of the large sphere, the small spheres occurs in many a clayey railway-cutting, as railway-engineers are on the point of being pulled apart ; then c is the approxima. know too well. There seems to be no occasion for importing!

tion to Roche's limit. G. R.'s condition is that the excess of the the notion of "faulting" of the rocks themselves into the attraction of the large sphere on the nearer small one above the question. Suill less rational is the notion that vibrations due attraction on the further one is equal to the attraction between to the blowing-up of one or iwo ships lately had anything to do the small ones. In algebraical language this becomes with the catastrophe. The most elementary principles of mechanics explain it completely.

A mass of rock-Tragments and clayey material, such as may constitute a "scree," acquires in time a certain amount of co. Wher ce herency from the oxidation of the irony constituents, or from the

(22 – 12,= 16R3 D. solution and redeposition of carbonate of lime (where the materials are calcareous) by carbonated atmospheric waters percolating the mass, or from both of these causes. If the mass is Treating r as very small we have c = 2:52 R X (D/d). fairly drained internally it may retain its stable condition for If the spheres r are not very small, if D=d, and if R be taken any length of time, and be mistaken for a part of the solid as unit of length, the equation for c becomes geotectony of the district, though in cases where the materials are largely composed of decomposable silicates, it is evident that

Ft - 2122 - 16€ + gut = 0. there is a tendency for the proportion of the fine slippery clay. material in the mass to increase. The consequence may be (and

This quartic determines the approximate limit when the often is) that there is a tendency in the whole mass to settle down

ñ satellite is not infinitely small. under the force of gravitation, and so a slow preliminary differen.

I shall now use this equation to find what size we must attri. tial movement often goes on for years, before some new factor is 1 La figure d'une masse fluide soumise à l'attraction d'un point élointroduced to precipitate the disa ter. There can scarcely beginé," E. Roche. ad des Sci, de Montpelier, vol. i. (1847-50), p. 243.

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