July A,, 1889] 



NA TURE 



22 



for Darwin, whilst against them were ranged L. Agassiz, LeConte, 

 Hunt, Semper, and Rein. One might with equal justice claim 

 for an eminent engineer that a bridge canstructed by him as a 

 young man in 1842 and repaired by him when an elderly man in 

 1874, represented the accumulated experience of a long profes- 

 sional career, notwithstanding that he had never since erected 

 another bridge, and had devoted all his time to works of a very 

 different character, and in spite of the fact that, whilst only two 

 engineers of reputation had in the interval pronounced the bridge 

 to be safe, five others of equal eminence had advised that, owing 

 to its rickety condition, it should be pulled down. If it was a 

 question of personal safety, most people would trust to the 

 opinion of the many. 



1 will first clear the way by laying stress on the circumstance 

 that neither A. Agassiz nor Murray doubt the reality of subsid- 

 ence. They only contend that the characteristic form of atolls 

 and barrier reefs is not dependent on it, and that such reefs 

 would be produced by their natural mode of growth alone. 



Now, with regard to Fiji, Captain Moore is perhaps not aware 

 that in the writings of Murray, Semper, Geikie, and others, in 

 these columns and elsewhere, the association of the three classes 

 of reefs in the same group, as in Fiji, has often been referred to 

 as opposed to the theory of subsidence. It was the occurrence 

 of all reefs in the Fijis and in the Pelew Group, and the ascertained 

 existence of upraised reefs in the last locality, that amongst other 

 reasons led Murray and Semper to find some different explanation 

 than that of subsidence. Dana saw the difficulty, and tried to 

 avoid it by asserting that small fringing reefs are "often evidence 

 of subsidence, even a greater subsidence than is implied by barrier 

 reefs" {Avter. Jonrn. Science and Arts, 3rd series, vol. viii., 

 p. 316). Semper, however, pointed out that this conclusion at 

 once destroyed the value of the testimony afforded by coral reefs 

 of the movements of the earth's crust, since, if all kinds of reefs 

 can be formed during subsidence, the character of a reef cannot 

 guide us in determining the existence of subsidence or upheaval 

 (" Animal Life," p. 233). Darwin also saw the difficulty of the 

 Pelew Group, where living atolls, barrier reefs, and fringing reefs 

 were associated with upraised ancient reefs ; and thus it came 

 about that, when writing to Semper in 1879, he generously ob- 

 served that, although he still adhered to the theory of subsidence, 

 such cases as that of the Pelew Islands, if of at all frequent occur- 

 rence, would make his conclusions of very little value. "Future 

 observers," he went on to say, "must decide between us," &c. 

 (Semper's "Animal Life," p. 456). 



I contend that in 1889 Mr. Darwin's condition has already 

 been realized, since we have in the interval proved that in respect 

 to the occurrence in the same locality of all three classes of coral 

 reefs and their association with ancient upraised reefs, the Fijis, 

 the Tongan Group, and the Solomon Islands are but reproduc- 

 tions of the Pelew Group. It will therefore be seen that Captain 

 Moore is in error when he believes that Darwin would not have 

 regarded simultaneous up and down movements in the same 

 group as inconsistent with his theory. Darwin's admission to 

 Prof. Semper in the case of the Pelews shows plainly enough 

 what he would have thought of the Fijis. This difficulty of 

 imagining simuhaneous up and down movements in the same 

 group was also perceived by the present Director- General of the 

 Geological Survey, when he remarked some years ago in these 

 columns that " such an association of upheaval with an assumed 

 general subsidence requires, on the subsidence theory, a cumbrous 

 and entirely hypothetical series of upward and downward move- 

 ments " (Nature, vol. xxix, p. 107 ; Proc. Roy. Phys. 

 Soc. viii.). 



It is soniewhat remarkable that long as the Fiji Group has been 

 known, it is only of recent years that anything has been published 

 concerning its upraised coral reefs and its other evidences of con- 

 siderable upheaval. Darwin, as late as his edition of 1874, knew 

 nothing of the extensively upraised reefs, and he still coloured 

 the group in his map as in an area of subsidence. Strangely 

 enough, amongst the many errors perpetuated in the edition 

 published in the present year of Mr. Darwin's work, is that re- 

 lating to this group. In an additional footnote (p. 215) we find 

 no reference to the ancient coral reefs upraised some hundreds of 

 feet in the Lau or Windward Group, which are referred to in the 

 Hydrographic publication of 1882 concerning Fiji, and which 

 were described to me by Lieut. Malan some years ago. We find 

 no reference in this edition of 1889 to the conclusion of Mr. Brady 

 that the Suva soapstone, as indicated by its Foraminifera, was 

 formed in depths of from 150 to 203 fathoms in post-Tertiary 

 times, thus jmplying an upheaval of from 900 to 1200 feet 



(Geol. Soc, November 9, 1887). Curious as it may appear, 

 Dana, after his lengthened stay in the group, found proofs of an 

 elevation in the larger islands of only 5 or 6 feet, and was 

 inclined to negative it altogether in the case of the eastern islands 

 ("Corals and Coral Islands," 1872, pp. 342, 346). 



Captain Moore refers to the " many evidences of upheaval" in 

 Fiji, and instances the occurrence of shells and coral "at great 

 heights." What evidence has he of subsidence ? He points to 

 the form of the reef in various islands, and thus assumes the very 

 question at issue. However, I will leave to Mr. Murray to ex- 

 plain how these reefs attained their characteristic form without 

 the assumed movement of .subsidence, of which in fact we can 

 find no direct proof. H. B. GUPPY. 



As Dr. Guppy asks for information with regard to the corals 

 found living at the greater depths round islands in the Indian 

 and Pacific Oceans the followinsj may be of interest. 



About two years ago Capt. Wharton, P\R. S., called attention 

 to the Tizard Bank, and last year both it and the Macclesfield 

 Banks were examined by H.M.S. Rambler. 



The further investigation of the material sent home has shown 

 that the large number of eighteen genera with forty species were 

 found living in depths from 20-44 fathoms outside the reefs, 

 and these species differed with but few exceptions from those in 

 the shallow water. 



The following ten genera were found at a greater depth 

 than 30 fathoms — Stylophora, Astrasa, Pavonia, Cycloseris, 

 Leptoseris, Stephanaria, Psammocora, Montipora, Alveopora, 

 and Rhodarcea, besides seven small scarcely reef-building genera. 



The total number of speci:;s collected was 142, so that nearly 

 one-third were represented in over 20 fathoms. 



I'. W. Bassett-Smith, R.N. 



Hibernation of Martins in the Argentine Republic. 



Prof. Carlo Spegazzini, an Italian botanist, and quite a 

 trustworthy observer, living at La Plata, the new town in the 

 Argentine Republic, writes from there the following account to 

 my friend the Marquis Giacomo Doria of Genoa : — 



"The bird known here by the name of Golondritia, and 

 which I think is Prague domestica,'^ is subject to hibernation. 

 Last year, while the zinc roof of a small house was being taken 

 up in the month of August, just in the middle of our winter, I 

 found underneath about a hundred martins, all accumulated one 

 over the other and lethargic, but in good health, so that, exposed 

 to the sun, they awoke and flew away very briskly. This year, 

 again, having seen some holes on a barra>icha, a steep bank over 

 the Plata, I began to dig at them, hoping to find some bats ; 

 but there I found several hundreds of the martins of the same 

 kind as above mentioned, clustered and in a state of lethargy. 

 Is such a thing known to naturalists ? " 



TOMMASO SaLVADORI. 

 Zoological Museiim, Turin, June 18. 



.Atmospheric Electricity. 



The interesting accounts of certain electrical phenomena of 

 the atmosphere in Nature of May 16, 23, and 30, lead me to 

 state that it is a common experience of surveying parties, es- 

 pecially on the high peaks and slopes in the western part of this 

 country to undergo these peculiar electrical sensations. In 

 general these maybe described as tingling or pricking sensations, 

 accompanied with hissing or crackling sounds, especially marked 

 if a finger be presented to any metallic object near by. But 

 further than this it has been noticed that whenever a flash of 

 lightning occurs there is a sudden cessation of the distressing 

 electrical effects. The explanation of this is, we think, found in 

 some experiments made at the top of the Washington Monument 

 (elevation 500 feet) during thunderstorms. With a " water 

 dropper collecter," Mascart insulators and quadrant electrometer, 

 we measured the difference of the electrical potential of the air 

 and the ground. The electrometer needle becomes very active 

 with the approach of the " thunder-heads," and after consider- 

 able oscillation begins to move steadily in one direction as if 

 subjected to a steadily increasing "pull," and then suddenly, 

 when a potential difference of several thousand volts may be 

 indicated, there is an "instant" drop to zero, and apparent 

 rebound in the other direction, not due to the torsion of the 

 ■ Or more likely Prague chalybcca, Gm.— T. S. 



