May, 1904.] 



KNOWLEDGE & SCIENTIFIC NFAVS. 



09 



then assail it as a factor in the argument ? If, on the other hand, 

 the Darwinian theorj- be assailed on other than dialectic or 

 theological grounds, then the tirst necessity is to be scrupu- 

 lously fair, meticulously exact. W'c have not sp.ace to consider 

 critic.-iUy all the quotations which Mr. Gerard brings forward 

 as evidence against it : but we may briefly refer to one part of 

 his case, which is contained in the chapters on the geological 

 record. He (piotes with approval the attacks which Mr. 

 Carruthcrs made in 1S76 .as President of the Geologists' Asso- 

 ciation, and later in book form (iSySl, on the incompleteness of 

 the bot.anieal fossil record, and its failure to show any connect- 

 ing link between the greater divisions of plants. But Mr. 

 Gerard entirely ignores the work which has been done since 

 iSgS by Professor A. O. Seward, Dr. 1). H. Scott, and Pro- 

 fessor F. W. OUver in fossil botany, and the opinions expressed 

 by them. To quote but a single instance: Dr. D. H. Scott 

 and Professor F. W. Oliver have within the last twelve months 

 shown reason for connecting the Ferns with the Cycads; and 

 have exhibited in Lyginodendron a seed-bearing fern. Not, 

 however, to go into too great detail, we may quote from Pro- 

 fessor Seward's British Association address an observation 

 made by Darwin himself on the imperfection of the geologic 

 record, " The crust of the earth, with its embedded remains. 

 must not be looked at as a well-filled nniseum. but as a poor 

 collection made at hazard and at rare intervals." And the 

 transitions of form and species are not incompatible with evo- 

 lutionary theory. 



A Chemical Conceptiun of the litlier. 15y I'rofessor I). 

 Mendelceff. (London : I^ongmaus, Green, and Co.) The 

 discovery of the radio-active properties of some of the metals. 

 and the probability which Lord Kelvin remarked, that most 

 substances are radio-active to a greater or less extent, has 

 been one of the corroborative facts to sustain the electro- 

 atomic theory of matter. That theory has been hesitatingly 

 received by many chemists, who have not hesitated to dispute 

 the objeeti\e reality of atoms — regarding them merely as 

 vehicles for expressing relations between the elements — and 

 who have seen in the extension of the theory so as to take in 

 "atoms of electricity" or "electrons," or "twists in the 

 ether," an unprovable hypothesis which they do not need to 

 explain chemical inter-action. The attack on the physicists' 

 conception of the atom of matter as an imperceptibly small 

 system of forces in which electrons revolve at enormous speeds 

 and possibly in concentric rings (not unlike a solar s3'stem in 

 miniature, or the rings of moons about the pl.met Saturn) has 

 not hitherto been very well directed. It has in at least one 

 instance put forward an untenable explanation of some of the 

 facts of radiation ; and while ignoring the fact that the 

 •■ electron " theory does explain the radiation of radium and 

 thorium very well, has offered no alternative theory. Pro- 

 fessor MendeleefTs theory of the ether removes, however, the 

 latter reproach, and offers a supposition which, though await- 

 ing the test of mathematical examination on the part of the 

 physicists, is an extremely interesting one. He boldly sweeps 

 away the anomalies of believing the ether to be an all- 

 per\'ading substance — rigid as steel, yet interpenetrating all 

 matter; frictionless, but without weight — by imagining it to be 

 a gas that has weight and substance, though it is of such 

 extreme tenuity that it is capable of interpenetrating .ill 

 other substances and incapable of offering a measurable 

 resistance to their passage among its molecules. Its in- 

 susceptibility to chemical combination is to be regarded as 

 similar to a similar inertia on the part of helium or argon, or 

 the gas emanating from radium ; its imponderabihty is not 

 real, but due merely from the absence of an)' known means of 

 weighing it. Professor Mendelceff calculates that this theory 

 w'ould fulfil the requirements mathematically demanded from 

 it if the ether, the lightest element, and its particles and atoms 

 had an atomic weight nearly one-millionth that of hydrogen, 

 and travelled with a velocity of about 2250 kilometres a 

 second. We need not follow Professor Mendeleeff's theory 

 in all its details, but it will not be uninteresting to summarise 

 the way in which it responds to the demands put on it to 

 explain radio-activity. Although the ether, or, as he calls it, 

 the lightest of gases, x, has no power to form stable chemical 

 compounds, it would not be deprived of the faculty of dis- 

 solving in, or accumulating about, large centres of attraction 

 — like the sun among heavenly bodies, or the heavy uranium 

 and thorium atoms. If the ether be a gas x it must naturally 



accumulate from all parts of the universe towards the heavy 

 suns, just as the gases in the atuiosphcre accumulate in a drop 

 of water. Similarlv it will acemnul.ile towards the heaviest 

 atoms of thorium or uranium. 1/ siuli ii spcciiil acciimiilitl'uin 

 of ctlur atoms iihoiit tlu- iiioleciilcs of rndium and thorinin lie 

 adiiiissihlejlicij mifiht lie expcctid to cxiiiint fccuUar phenomena 

 dctci-mincd by the emission of 11 portion of this ether held hy 

 partielen of normal mean vehicily and by new ether enlerinf; 

 into the sphere of attraction. In short, the theory of tlic great 

 Russian chemist is not unlike in form that explanation sug- 

 gested l>v Sir William Crookes and Dr. Johnstone Stoney, .-ind 

 partly confirmed by Lord Kelvin, that the radiation of radium, 

 thorium. lS:c., is sustained by energy from without rather than 

 from within. 



The lissential Kaffir. II is to the human interest of the 

 Kafhr that Mr. Dudley Kidd devotes himself in his valuable 

 and entertaining book, "The Essential Kaffir." (Adam and 

 Charles Black.) He uses the word Kaffir in its broadest 

 sense to include all the dark-skinned tribes of South Africa; 

 his information concerning the people of whom he writes is 

 intimate and varied, comprising the gleanings of a dozen years, 

 repeated visits to their tribes, visits in which he associated 

 with tliem in terms of intimacy, slept in their huts, watclied 

 thi-ir h.ibits of life and their social and religious customs, 

 memorialising them in many admiraljle and curious photo- 

 grai)hs which add greatly to the value .uid interest of his book. 

 There is, for instance, the photograph of the mother feeding 

 her baby with sour milk out of her hand, while a lean dog 

 watches the operation with symp.ithetic inteiest. In the next 

 ])hotogr.iph the dog is buing utilised as a napkin to lick the 

 b.iby's face clean, while the mother holds its unwilling counten- 

 ance- steady with one hantl while she guides the dog's head 

 with the other. Mr. Kidd describes a night spent in a Kaffir 

 hut in company with the Kaffir family and such household 

 pets as a e.alf, a dog, roosting fowls, and others who shall be 

 nameless, but who could scale even sandbanks of Keating. 

 One feels as one reads that self-sacrifice in the cause of know- 

 ledge could go no further. Very interesting are the chapters 

 on Kaffir mental characteristics, on their nmsical instruments 

 and games, and on their religious beliefs. Of their mental 

 powers he notes the curious fact that the native children some- 

 times absorb knowledge with a singular precocity, but as they 

 develop their brains, as it were, seem to stop growing, tlieir 

 energies appear to be absorbed in their bodily development, and 

 whether caused by " meclianical formation of the bones of the 

 skull or not, must fie left to men of science to settle ; yet the fact 

 of stunted mental development remains." At the same timi' 

 the natives are remarkable for their extraordinary memory of 

 facts which interest them, such as the precedents in a legal 

 case. In a book where every page is interesting, an adequate 

 idea of its contents can hardly be given in so short a space. 

 All such people as the Kaffirs here described must rapidly 

 lose much of their individual character in contact with other 

 civilisations, and a book th.it crystallises their essential charac- 

 teristics from intimate observations lias a more than ephe- 

 meral interest. 



Physical Chemistry in the Sciences, by Jacobus Vaii't Hoff. 

 (Chicago: The University Press.) To the Decennial publica- 

 tions of the University of Chicago have been added the series 

 of lectures which were delivered there by the German chemist, 

 Van't Hoff, and which deal with " Physical Chemistry in the 

 Service of the Sciences." The lectures, lucid, terse, concen- 

 trated, deal with Physical Chemistry in Pure Chemistry, in 

 Physiology, in Geology, and in Industrial Chemistry. T'loni 

 the last-named cliapter we may make an cxtnact which should 

 be very serviceable in bringing home to the British nation the 

 true reason for the growing strength of the German competitor 

 in industries that for many years were chiefly British. " There 

 exists in Germany," says Van't Hofi', " a very beneficial co- 

 operation between laboratory work and technical work. Both 

 go as far as possible hand in hand. After physical chemistry 

 had made several important advances, and was firmly estab- 

 lished in such a way th,al pure chemistry was assisted by co- 

 operation with it. Professor Ostwald judged correctly that this 

 co-operation would be valuable in teclinic.il directions. In this 

 beliefhe founded the I':iectro-Chemical Society. . . . All the 

 most conspicuous chemical industries of Germany are repre- 

 sented in the Society, which has its own organ of publication. 

 Nor has the stimulus to this co-operation come purely on the 



