344 



♦ KNOWLEDGE ♦ 



[Jdne 8, 1883. 



little moro tlian time to got there and back, in the form of 

 a recent definite recourse to corsets — now, when 1 am 

 considerably past the age at which every man is either 

 a fool or a physician. 



Naturally, my good friends of the ^Melbourne press 

 make some little fui\ of this tlirec-black-crows item of news. 

 I should l)e fair game, were it true. If it is of any interest 

 to them (as ajiparently it is) to note such matters, I may 

 mention that when I made the e.xperiment in question, 

 ttrelvc years before my visit to Australasia, I weighed 

 14 St. 7 11)., whereas during the time of my visit to them I 

 drew but 11 st. 10 lb. ; and even now only V2 st. 6 lb. 



A LETTER in the Times, signed C. Pritchard, presumably 

 from the Rev. Charles Pritchard, Savilian Professor of 

 Astronomy at Oxford, speaks of the advantage of the 

 study of the Greek language. Mr. Pritchard's repugnance 

 to a scheme by which the degree of Bachelor of Natural 

 Science might be obtained without the necessity of pass- 

 ing a previous examination in Greek, arose, it appears, 

 " from a life-long experience of the educational advantages 

 derivable from a study of the Greek language and litera 

 ture." The world had, it seems, "misapprehended the 

 motives which induced some of us Museum Professors to 

 vote against " that scheme. " I, with others," says Mr. 

 Pritchard, " felt that it was an invidious thing to single 

 out us poor science men as the only university students 

 desirous of escaping Greek." Whether Professor Adams 

 or Professor Cayley, or, in fact, any university professor 

 who has made a name in science, would trouble himself to 

 express strong repugnance lest he, not being a " poor " 

 science man, should be suspected of ignorance of Greek, 

 is a question which may occur to some who know how 

 very much one professor differs from another in distinction. 

 One can imagine {apropos des holies) that ^Esop's daw, 

 conscious of questionable tail-feathers, might have insisted 

 on the beak as a feature which a life-long experience had 

 taught him to regard as all-important among b irds. 



Seriously, if the opinion of science is to be taken on 

 the question of the study of Greek by those who go in 

 for degrees in Natural Science, one would like to have the 

 opinion, not of " poor" science men, but of the real men of 

 science who honour the universities by holding professor- 

 ships there. Professor Adams, co-discoverer of Neptune 

 with the great Leverrier, Professor Cayley, the greatest 

 master of pure mathematics living, and men of like 

 standing, are rather annoyingly silent on this subject; 

 Professor Pritchard, author of ? — , discoverer of ? — , in- 

 ventor of 1 — , but promiser of new lunar theories, and like 

 loud-sounding nothings, is scarce less annoyingly voluble. 



Still, Professor Pritchard's exceptional familiarity with 

 Greek language and literature may, perhaps, entitle him to 

 speak. I remember once, when a new and atrocious addi- 

 tion to astronomical nomenclature was under discussion 

 before the Astronomical Society, I objected strongly, and I 

 am glad to think effectively, to the proposed word — leuco- 

 sphere (or white sphere)— on the ground, among other more 

 important reasons, that the word, judged by its sound, would 

 be mistaken for wolf-sphere ; on which I was told by Pro- 

 fessor Pritchard, considerably to my astonishment, that the 

 Greek for a wolf was "not \iiKi,r, but Xi-nr." This singular 

 discovery was perhaps one of the results of "a lifelong 

 experience of the educational advantages arising from a 

 study of the Greek language and literature." Professor 

 Pritchard must be almost as well fitted to speak with 

 authority on this point as on questions suited to " poor 

 science students." 



Erbi'ririsf. 



THE PAST OF OUR EARTH.* 



By JticiiARD A. Phoctob. 



THIS would not be the place for a review, properly so- 

 called, of the masterly treatise before us, full as it is 

 of matter which, though exactly described and dealt with, 

 cannot be said to be plainly worded. So far as this book 

 is to be regarded as a mathematical treatise, it is outside 

 our lines ; we need only note that the mathematical treat- 

 ment of the subjects dealt with is thorough and admirable, 

 and even that will be no news to those whom it alone 

 concerns — advanced mathematicians — seeing that the 

 names of Professors Thomson and Tait are a guarantee 

 for profound and accurate investigation of all subjects 

 falling within the range of mathematical inquiry. 



But matters are dealt with in this work, which, though 

 here treated in a way which only mathematicians can 

 follow, are full of interest to all students of science. Among 

 these are (1) the subject of the tides, admirably dealt with 

 in the present work, in sections 798-811 ; (2) the effects of 

 tidal friction (sections 830, 8-31, and Appendix G) and 

 their connection vrith w-hat is commonly termed the lunar 

 acceleration, though analogy would suggest the use of 

 another expression! ; (3) the condition of the earth's 

 interior (sections 832-8-16 ; (4) the secular cooling of the 

 earth ; (.5) the age of the sun's heat ; (6) and the size of 

 atoms. 



In dealing with the cooling of the earth. Professor 

 Thomson maintains that, on the whole, there is reason for 

 regarding as probable those geological speculations which 

 assume somewhat greater extremes of heat, some violent 

 storms and floods, more luxuriant vegetation, and hardier 

 and coarser-grained plants and animals in remote antiquity. 

 " A middle path," he says, "though not generally safest in 

 scientific speculations, seems to be so in this case. It is 

 probable that hypotheses of grand catastrophes, destroying 

 all life from the earth, and ruining its whole surface at 

 once, are greatly in error; " but, on the other hand, "it is 

 impossible that hypotheses assuming an equality of sun and 

 storms for 1,000,000 years can be wholly true." 



In the same interesting portion of the work before us, 

 Sir W. Thomson, speaking of an opinion advanced by Sir 

 Charles Lyell, respecting the possible maintenance of the 

 earth's heat without change throughout countless ages, 

 uses words which may be applied without change of a word 

 to the stupendous theory advanced by Sir C. Siemens not 

 so very long since — such an idea of a practically endless 

 cycle " violates the principles of natural philosophy in 

 exactly the same manner, and to the same degree, as to 

 believe that a clock constructed with a self-winding move- 

 ment may fulfil the expectations of its ingenious inventor 

 by going for ever." The earth is necessarily cooling from 

 century to century ; her volcanic energies are certainly 

 diminishing, as certainly, to use an illustration of Sir W. 

 Thomson's, as the quantity of gunpowder in a " monitor " 

 is diminishing when hour after hour she is seen to discharge 



* " Treatise on Natural Philosophy." By Professors Sir W. 

 Tliomson and P. G. Tait. Tol. I., Part II. (Cambridge University 

 Press.) 



t It is well pointed ont by onr authors that the ordinary use of 

 the expression " lunar acceleration " is as incorrect as would be the 

 use of the word " acceleration " to describe the fall of a body in 

 whatever period is taken as the unit of time, and the cnmraon but 

 really absurd mistake of speaking of a clock as so many seconds or 

 minutes fast, when in reality it is only by so much in advance of 

 true time. The authors of the work before us suggest the use of 

 the words " lunar advance " to express what has hitherto been 

 erroneously called " lunar acceleration." 



