94. 



■NA TURE 



{Nov. 2 2, 1888 



■might occur in rocks now coarsely crystalline. As time went 

 -on, true sediments would predominate over extravasated ma- 

 tferials, and these would be less and less affected by chemical 

 clianges, and would more and more retain their original charac- 

 ter. Thus we should expect that as we retraced the earth's 

 course through "the corridor of time," we should arrive at rocks 

 -which, though crystalline in structure, were evidently in great 

 part ' sedimentary in origin, and should beyond them find rocks 

 ■of more coarsely-crystalline texture and more dubious character, 

 'which, however, probably were in part of a like origin ; and 

 •should at last reach coarsely-crystalline rocks, in which, while 

 occasional sediments would be possible, the majority were 

 originally igneous, though modified at a very early period of 

 their history. This corresponds with what we find in Nature, 

 when we apply, cautiously and tentatively, the principles of 

 interpretation which guide us in straligraphical geology. 



I have stated as briefly as possible what I believe to be 

 •facts. I have endeavoured to treat these in accordance with 

 the principles of inductive reasoning. I have deliberately 

 :abstained from invoking the aid of "deluges of water, floods 

 of fire, boiling oceans, caustic rains, or acid-laden atmospheres," 

 not because I hold it impossible that these can have occurred, 

 but because I think this epoch in the earth's history so remote 

 and so unlike those which followed, that it is wiser to pass it 

 by for the present. But unless we deny that any rocks formed 

 anterior to or coseval with the first beginning of life on ihe 

 globe can bs preserved to the present time, or, at least, be 

 ■capable of identification (an assumption which seems to me 

 -gratuitous and unphilosophical) then I do not see how we can 

 avoid the conclusion to which we are led by a study of the 

 foundation-stones of the earth's crust — namely, that these were 

 ■formed under conditions and modified by environments which, 

 ■tluring later geological epochs, must have been of very excep- 

 tional occurrence. If, then, this conclusion accords with the 

 ^results at which students of chemistry and students of physics 

 have independently arrived, I do not think that we are justified 

 in refusing to accept them, because they lack the attractive 

 brilliancy of this or that hypothesis, or do not accord with the 

 ■words in which a principle, sound in its essence, has been 

 formulated. It is true in science, as in a yet more sacred 

 sthing, that "the letter killeth, the spirit giveth life." 



in all the characters in which it so strongly approaches the 

 Mallophaga it offers merely an illustration of modification due to 

 food, habit, and environment. In this particular it is, however, 

 of very great interest as one of the most striking illustrations we 

 have of variation in similar lines through the influence of purely 

 external or dynamical conditions, and where genetic connection 

 and heredity play no part whatever. It is at the same lime 

 interesting because of its synthetic characteristics, being evidently 

 an ancient type, from which we get a very good idea of the 

 connection in the past of some of the present well-defined 

 orders of insects." 



SYSTEM A TIC RE LA T/OA'S OE FLA TY- 

 PSYLLUS AS DETERMINEDBY THE LARVA. 

 iTDROF. C. V, RII.EY, in a paper read at a recent meeting of 

 ^ the National Academy of Science (U.S.A.), drew attention 

 to the unique character of Platypsyllns castoris, a parasite of the 

 beaver ; and gave an epitome of the literature on the subject, 

 shov^in^ how the insect had puzzled systematists, and had 

 been placed by high authority among the Culeoplera and the 

 ^Mallophaga, and made the type even of a new order. He 

 showed the value, as at once settling the question of its true 

 •position, of a knowledge of the adolescent states, He had had 

 •since November i886 some 14 specimens of the larva, 

 obtained from a beaver neaj: We,st Point, Nebraska, and had 

 recently been led to study his material at the instance of 

 Dr. Geo. H. Horn, of Philadelphia, who at a recent meet- 

 ing of the Entomological Society of Washington announced 

 the discovery of the larva by one of his correspondents the 

 present spring, and will publish a full description of it. Prof. 

 Riley indicated the undoubted Coleopterological characteristics 

 of the insect in the imago state, laying stress on the large 

 scutellum and five-jointed tarsi, which at once remove it from 

 the Mallophaga, none of which possess these characters. He 

 also showed that the lai-va fully corroborates its Coleopterological 

 position, and that its general structure, and particularly the trophi, 

 anal cerci, and pseudopod, confirm its Clavicorn affinities. He 

 showed that the atrophied mandibles in the imago really existed as 

 described by Le Conte, and that even in the larva they were 

 feeble and of doubtful service in mastication. He mentioned, as 

 -confirmatory of these conclusions, the finding by one of his 

 agents, Mr. A. Koebele, of Leptinillus Uhe Cole >pterological 

 nature of which no one has doubted, and the nearest ally to 

 Platypsyllus), associated with Platypsyllus upon beave -skins from 

 Alaska ; also the parasitism of Leptinus upon mice. He paid a 

 high compliment to the judgment and deep knowledge of the late 

 Dr. Le Conte, whose work on the imago deserves the highest 

 praise, and whose conclusions were thus vindicated. "Platy- 

 psyllus therefore," he concluded, "is a good Coleopteron, and 



SCIENTIFIC SERIALS. 



Atti della R. Accadania del Lined, July and August 1888. — 

 In both of these numbers G. Vicentini and D. Omodei continue 

 their important inquiries on the thermic expansion of certain 

 binary alloys in the liquid state. So far they have arrived at 

 the following general conclusions : (i) the variation of volume 

 accompanying liquid metallic mixtures is extremely slight ; 

 (2) no relation can be established between the variations of 

 volume that accompany the formation of alloys in the solid and 

 liquid states ; (3) the variation of density at the moment of 

 solidification is in general less than would be the case were the 

 constituent metals to preserve in the alloys the value that they 

 possess in the isolated state ; (4) fhe binary alloys of lead and 

 tin, of tin and bismuth, and of tin and cadmium, possess in 

 the state of perfect fusion an expansion equal to that resulting 

 from the sum of the expansions of the associated metals ; (5) 

 the alloy of Bi.^Pb possesses a coefficient of expansion far greater 

 than the sum of the expansions of the constituent metals. These 

 experiments, which conclude for the present with a preliminary 

 study of the antimony and zinc alloys, have been carried out at 

 the physical laboratory of the University of Cagliari, Sardinia. 



Rivista Scientifico-Industriale, October. — Experiments made 

 with Crookes's radiometer, by Prof. Pietro Lancetta. The 

 experiments here described have been undertaken chiefly for the 

 purpose of making a synthesis of certain phenomena which are 

 more easily produced by this apparatu.s than by any other means. 

 It is also shown that the radiometer may in some cases be more 

 advantageously employed than the ordinary thermometer, 

 especially in testing certain laws regarding latent and luminous 

 heat, Crookes's instrument being sensible both to the dark and 

 luminous wave of the solar rays. The results of the experi- 

 ments show generally that in a homogeneous medium the 

 radiation of the thermo-luminous wave is propagated in a 

 straight line ; that the luminous wave is propagated in vacuo ; 

 that the intensity of the thermo-luminous wave is in inverse ratio 

 to the square of the distance ; that the evaporation of fluids as 

 well as the rarefaction of gaseous bodies is accompanied by a 

 lowering of the temperature, while the condensation of gas 

 develops heat. 



Jon7-nal of the Russian Chemical and Physical Society, vol. xx, 

 fasc. 6. —On the speed and the products of decomposition of the 

 chlorate and chlorite of lithium, by A. Potilitzin, being the second 

 part of an inquiry into the properties of galloid compounds. 

 The decomposition of the two above-mentioned salts, as well as of 

 the bromate of barium, is best explained according to the law of 

 unstable equilibrium indicated by the author in his former works, 

 and which he sums up as follows : in each chemical reaction the 

 equilibrium of the system depends upon the values of their 

 atomic weights, their n-jasses, and their stock of potential 

 energy. — On the relation between the rotatory power and the 

 refraction of organic compounds, by J. Kanonnikoff, first part. — 

 On the action of organic iodides on natrium-nitro-ethane, by N. 

 Sokoloff. — Obituary notice of Prof. Wroblewski, by S. 

 Lamansky. — The total eclipse of the sun of August 19, 1887, by 

 N. Egorotf; and on the results of meteorological observations 

 during the same eclipse, by N. Hesehus. 



SOCIETIES AND ACADEMIES. 

 London. 

 Royal Society, May 31. — "On the Effect of Occluded 

 Gases on the Thermo-electric Properties of Bodies, and on their 

 Resistances; also on the Thermoelectric and other Properties 

 of Graphite and Carbon." By James Monckman, D.Sc. 

 Communicated by Prof. J. J. Thomson, F. R.S. 



