May 6, 1880] 



NATURE 



23 



above the galvanometer, vihich conbitts of a copper ribbon 

 making some twenty turns round a pair of astatic needles im. 

 long and | in. broad, pivoted in an agate cup. A contact-key is 

 placed on one side, and the whole is inclosed in a glass shade 

 perforated opposite the pile. A glass cone protects the front 

 from extraneous heat, and a glass case the back. A directing 

 magnet is fixed above the pile. Contact betueen the galvano- 

 meter and pile is made after (say) 30 seconds' exposure to the 

 heat. The pile is aflfected by a person standing six feet from it, 

 and the radiation from stellar space is evident in clear v\ eather. 

 Half a minute is sufficient to put the instrument ready for use.— 

 Jlr. Ridout also exhibited laboratory experiments showing 

 cohesion in mercury by causing it to overflow up an inclined 

 trough ; electrolysis of water by a single Grove or bichromate 

 cell, through diminishing the pressure in the flask containing the 

 water by broiling it and condensmg the vapour on cooling ; a 

 differential thermometer showing absorption of heat on lique- 

 fyinT solids ; and the production of musical notes in glass tubes 

 by c'ontracting the bore smoothly to about \ of the diameter at 

 one part. Prof. Foster remarked that the cohesion experiment 

 might sliow the surface-tension. Trof. Guthrie and Prof. Hughes 

 offered remarks on the electrolytic experiment, the latter stating 

 that he finds the resistance of an hon cell he has constructed to 

 depend on the electrodes rather than the liquid ; when the nega- 

 tive plate is tempered iron the resistance is low, when soft iron 

 it is high.— Prof. Stone exhibited photographs of Konig's nevif 

 tonometer described by him at the last meeting, and further 

 mentioned that Konig had devised a thermometer ba-ed on the 

 principle that changes of temperature produce corresponding 

 changes in the vibration rate of a tuning-fork. The temperature 

 is found from the rate of the fork by bringing it to a zero rate 

 by means of a rider. — Prof. Michin then described his experi- 

 ment to solve the problem of transmitting light by photo-electric 

 action. Two years ago he conceived the idea of employing for 

 this purpose the fact that hght falling on a sensitised silver plate 

 disengages electricity. He forms a sensitive cell composed of 

 two silver plates immersed in a conducting solution ; one plate 

 is coated with a sensitive emulsion of chloride or bromide of 

 silver. When chloride is used, a solution of salt in water forms 

 the liquid ; when bromide, a solution of bromide of potash. A 

 current is set up in the cell even in the dark, but when exposed 

 to the magnesium light the current is very powerful, and flow s 

 within the cell from the uncoated to the sensitised plate. Prof. 

 Micliin also conducted this current by wire to a second cell in a 

 dark chamber, and found that it effected a decomposition of the 

 sensitive plate in that cell, as shown by a distinct darkening of 

 the plate when "developed" by pyrogallic acid. The same 

 effect was produced whether the current was reversed or not. 

 Prof. Michin is continuing his experiments, and has provided a 

 cable containing a number of separate conductors insulated 

 from each other, in order to convey the currents from several 

 cells. Prof. Pen-y feared that the effect would not be strong 

 enough ; but Prof. Michin said the light of a match pro- 

 duced a decided photo-electric effect in the cell. Prof. Perry 

 alluded to the selenium plan proposed by himself and Prof. 

 Ayrton, and said that Mr. ^Yilloughby Smith had observed 

 selenium to be sensitive to the shadow^ of a flying swallow. 

 Prof. Adams testified to the sensitiveness of selenium and its 

 ]io\ver of being directly excited by light, a fact first proved by 

 the experiments of Mr. Day and himself. 



Entomological Society,' April 7. — H. T. Stainton, F.R.S., 

 vice-president, in the chair. — Messrs. G. C. Bignell, W. D. 

 Cansdale, Frank Crisp, and the Rev. W. Fowler, were elected 

 Ordinary Members, and M. E. Andre a Foreign Member. — 

 Mr. J. T. Carrington exhibited a pale variety of Arctta caja 

 which was bred by a gentleman at Croydon, who had been ex- 

 perimenting upon the effects' of the rays of light transmitted 

 through glasses of various colours upon this species. The speci- 

 men exhibited had been reared under green glass, but there was 

 no evidence to show that the variation was due to the green rays. 

 — The Secretary read a communication from Mr. Rothney, of 

 Calcutta, on insects destroyed by flowers, with reference to a 

 note on this subject published in the Proceedings of last year by 

 Mr. T. W, Slater. — The following papers were read: — Notes 

 on the coloration and development of insects, by Peter Cameron ; 

 on two gynandromorphous specimens of Cirrochroa aoris, Dbl., 

 an Indian species of mymphalideous butterflies ; and on Cetonia 

 aura'.a and Protactui bensoni, by Prof. Westwood. Specimens 

 and drawings ^^■ere exhibited in illustration of the last paper, 

 showing the specific distinctne?s of the insects in question. 



Meteorological Society, April 21. — Mr. G. J. Symons, 

 F.R.S., president, in the chair. — Rev. J. O. Bevan, M.A., 

 F. E. Cobb, E. Filliter, F.G.S., T. L. Gentles, W. A. Harri- 

 son, F.R.G.S., J. W. Peggs, F. Slade, and E. J. C. Smith, 

 were elected Fellows of the Society. — The discussion on Mr. 

 Ellis's paper, on the Greenwich sunshine records, 1876-S0, 

 was resumed and concluded. — The following papers were 

 read : — On the rate at which barometric changes traverse the 

 British Isles, by G. M. Whipple, B.Sc, F.R.A.S., F.M.S.— 

 A new form of Six's self-registering thermometer, by J. W. 

 Zambra, F.M.S. 



Edinburgh 



Royal Society, April £• — Sir Wyville Thomson, vice- 

 president, in the chair. — Mr. John Murray, of the Challenger 

 Expedition, occupied the evening v ith an interesting and 

 exhaustive paper on the structure and mode of origin of coral 

 reefs and islands. After detailing the well-known and widely- 

 accepted theory of Darwin, Mr. Murray proceeded to take 

 exception to its general truth, and to substitute a new theory, 

 which, in the light of the recent discoveries of the Challenger 

 Expedition, appeared at once simpler and more consistent with 

 the facts. The main features of this theory were as follows : 

 The abundant pelagic life of the ocean was stated to be the chief 

 food of the reef-building corals and of the deep-sea animals. 

 Lime-secreting creatures were especially abundant in tropical 

 oceanic w aters. Tow-net experiments showed that in a cubic 

 mass of the ocean one mile square by 100 fathoms, there were 

 about sixteen tons of carbonate of lime in the form of calcareous 

 Algee, Foraminifera, pelagic MoUnscs, &c. Although so abundant 

 on or near the surface the dead shells of these organisms were 

 quite absent from by far the greater part of the floor of the 

 ocean. In all the greater depths they were removed during 

 their fall or shortly after reaching the bottom by the actitjn of 

 carbonic acid, which was especially abundant in deep sea water. 

 Other things being equal, they were found at greater depths 

 where they were most abundant at the surface. On submarine 

 elevations (which were probably all of volcanic origin) these 

 dead shells were met with in great abundance : when the depth 

 was less than a mile ti-.e shells and skeletons of almost every 

 surface creature were present in the deposit. Mixed up with 

 these we had in these deposits the shells and skeletons of deep- 

 sea animals, as Echinoderms, Annelids, Polyzoa, Foraminifera, 

 Corals, &c. In these more or lessrshallow depths the accumula- 

 tion was relatively rapid, and the solvent action of sea water had 

 consequently little effect. Eventually this bank reached near 

 enough the surface to serve as a foundation for reef-buildhig 

 corals. As these corals built up to the surface those situated 

 towards the outer margin of the coral plantation had a great 

 advantage in the more abundant supply of food, and reached 

 the surface first. If the coral-field or plantation were small (less 

 than a square mile) the periphery was relatively large over which 

 food came from the ocean, and from which detritus was carried to 

 the interior ; hence the interior w as filled up and no lagoon w.is 

 formed. The same was the case when the coral plantation was 

 long and narrow. In larger coral-fields — the area increasing 

 as the square and the peripheiy only in an arithmetic progressi. 'n 

 —the interior parts of the coral plantation were at a relatively 

 great di-advantage, less food and less detritus for filling up we. e 

 supplied per square mile, and in consequence a lagoon was 

 formed. The carbonic acid in the sea water removed in solution 

 the lime of the dead coral and coral rock from the lagoon. As 

 the atoll extended seaw-ards the lagoon was widened and dcepent d 

 by the solvent and disintegrating pow er of the sea water. Ti e 

 structure of upraised coral atolls were referred to as confirmii g 

 these views. Barrier reefs were explained on the same pri - 

 ciples. Fringing reefs built seawards on a talus formed of th. r 

 own debris and of surface shells and deep-sea shells and skeletoirs,. 

 A lagoon-channel was gradually formed by the solvent action f 

 the sea water thrown over the reef at each tide. Inthisw:i/ 

 the fringing reef became a barrier reef. Numerous sections . .f 

 the reefs at Tahiti, from the survey of Lieut. Swire, of th-' 

 Challenger, were exhibited. The sUucture of the nitenor ove ■ 

 hanging reefs, and of the steep exterior submarine talus, wei 'j 

 especially pointed out and explained. The chief features of 

 barrier reefs and atolls were quite independent of subsidence, an i 

 would exist alike in stationary areas or in areas either of si 

 elevation or of slow subsidence. Throughout the volcanic islano ; 

 of the great oceans the evidence of recent elevation was ever> - 

 where conspicuous, and the same was the case in regions of barrier 



