July 15, 1875J 



NATURE 



223 



hlnus. Bos itrus, Cervus vugaccros, Ccrvus iarandus, Ovis, sp., 

 I?- 'kola, sp. 



Notes On Ilaytor Iron Mine, by Clement Le Neve Foster, 

 D.Sc. 



On the formation of the Polar Ice- cap, by Mr. J. J. Murphy. 

 The present paper is intended by the author to supplement a 

 previous one read before the Society in 1869 (Q. J. G. S., vol. 

 XXV. p. 350), in which he gave reasons for differing from Mr. 

 Crcll in thinking that the glacial climate was one of intense cold, 

 and held, on the contrary, that it was one of snowy winters and 

 cold summers, with a small range of temperature. Mr. Camp- 

 bell, in a paper read before the Society in 1874, gave the follow- 

 ing as the southernmost limits of the polar ice-cap, viz. :— In 

 Eastern Europe, lat. 56° N. ; in Germany, 55° ; in Britain, nearly 

 50° ; in America, 39°. This the author considers as strong but 

 not new evidence against the theory of ice-cap extending to low 

 latitudes ; the extent of the ice-eap would of course not be so 

 wide as that of the limits of glaciation, owing to the floating ice 

 approaching nearer the equator. After commenting on Mr. 

 Belt's remarks made during the discussion of Mr. Campbell's 

 paper, the author states that he attributes the presence of the 

 boulders found in the valley of the Amazon to icebergs which 

 had drifted further than usual. The glaciation of the tropics 

 would imply the glaciation of the whole world, which appears 

 no more possible than that the whole world was submerged at 

 one time. The author concludes with some remarks on a recent 

 paper of Mr. Tylor's. 



Notes on the Gasteropoda of the Guelph Formation of Canada, 

 by Prof II. Alleyne Nicholson, D.Sc, F.R.S.E. The author 

 notices the occurrence of the Guelph formation as a subdivision 

 of the Niagara series in Canada and the United States, and 

 describes it as consisting everywhere of a cellular, yellowish, or 

 cream-coloured dolomitic limestone of rough texture and crys- 

 taUine aspect, containing innumerable cavities from which fossils 

 of various kinds have been dissolved out. In this paper the 

 author describes all the known Gasteropoda of the Guelph for- 

 mation in Canada, including the following previously described 

 species : — Murchisonia Lo^anii (Hall), M. turritiformis (Hall), 

 M. macrospira (Hall), M. bivittata (Hall), M. longispira (Hall), 

 M. vitellia (Billings), M. Ilercyna (Billings), Cyclonema ? ele- 

 vata (Hall), Holopea guelplunsis (Billings), H. gracia (BiUings), 

 Subulites vc7ttricosus (Hall), and Pleurotomaria solarioides (Hall). 

 As new species he describes Murchisonia Boylei, distinguished 

 from M. turritiformis (Hall) and M. estella (Billings) by its more 

 rapid rate of expansion, its apparently canaliculated suture, and 

 the existence of an angular band a little above the suture ; and 

 Holopeal occidentalis, distinguished by its short but elevated 

 spire, its large body- whorl, which becomes almost disjunct at the 

 aperture, its circular aperture, and large umbilicus. The upper 

 whorls are convex, but the body-whorl is obtusely angulated 

 at about its upper fourth. Uncertain species of Murchisonia 

 and Pleurotomaria are also indicated. 



Description of a new genus of Tabulate Coral, by Mr. G. J. 

 Hinde. The coral described by the author as constituting a 

 new genus of Favositidae, for which he proposes the name of 

 SphcErolites, has a massive free corallum consisting of minute, 

 polygonal, closely united corallites, growing in all directions 

 Irom a central point, forming a spheroidal body, the entire sur- 

 face of which is occupied by the calices of the corallites. The 

 walls of the corallites are very delicate, with numerous pores ; 

 the tabula; are incomplete, formed by delicate arched lamellae, and 

 there are no septa. From Chcctetes this genus is distinguished 

 by the perforated walls and incomplete arched tabulae ; from 

 Favosites it differs in its mode of growth and its incomplete 

 tabulae ; and from Michdinia it is separated by the minuteness 

 of its coralUtes, and the absence of epitheca and of septal striiv. 

 The single species, which is named .S". Nicholsoni, is from cal- 

 careous shale of Lower Helderberg (Ludlow) age, near Dal- 

 housie, in New Brunswick. — {To be continued.) 



Physical Society, June 26 (continued from p. 179). — 

 Prof. G. ^C. Foster,J vice-president, in the chair. — Prof. G. 

 C. Foster called attention to the work of Prof. Everett 

 on the Centimetre-grarame-second (C.G.S.) System of Units 

 which will shortly bs published by the Society. It is 

 designed to facilitate the study of the quantitative rela- 

 tions between the different departments of physical science 

 by the adoption of a common system of units. Prof. Foster 

 explained that a committee of the British Association which 

 was appointed in 1872, and of which Prof. Everett was secretary, 

 recommended the adoption of this system, based upon the 



metric system, the unit of mass being the gramme, that oi length 

 the centimetre, and that of time the second. They recom- 

 mended that the unit of force be called a dyne, which therefore 

 is the force required to act upon a gramme of matter for a 

 second to generate a velocity of a centimetre per second. The 

 unit of work is called an erg, and is the amount of work done by 

 a dyne working through the distance of a centimetre. Prof. 

 Everett's book consists of a collection of physical data reduced to 

 these fundamental terms, so that no other physical magnitudes 

 enter into the expressions, and it cannot fail to prove of the 

 greatest possible value to physicists. Prof. Foster then left the 

 chair, which was taken by Dr. Stone. — Dr. W. .M Walts com- 

 municated a paper on a new form of micrometer for use in 

 spectroscopic analysis. In determining the positions of lines in a 

 spectrum by the use of a micrometer eye-piece or divided arc, 

 it is often difficult to see the cross wires distinctly without 

 admitting extraneous light, which with faint spectra fre- 

 quently cannot be done. Dr. Watts has sought to overcome 

 this difficulty by substituting some one known line of the 

 spectrum itself for the cross wires, and to measure the posi- 

 tions of unknown lines by bringing this index line successively 

 into coincidence with them. Thus, for example, the sodium 

 line, which is present in nearly every spectmm whether it is 

 wanted or not, may be made to move slowly when under the 

 spectrum, and the displacement necessary to make it coincide 

 with the lines to be measured may be determined by the read- 

 ings of a micrometer screw. To accomplish this a convex lens 

 of about two-feet focus is placed in front of the prism of the spec- 

 troscope, between the prism and observing telescope, and is 

 divided along a line at right-angles to the refracting edge of the 

 prism. One half of the lens is fixed, the other half is made to 

 slide over it by means of a micrometer screw. When the mov- 

 able half of the lens is in its normal position, the only effect is to 

 alter the focus of the telescope slightly, but when it is made to 

 slide over the fixed half, the refraction of the prism is increased 

 or diminished, and half of the spectrum appears to move over the 

 other half, and the sodium line, or any other convenient line of 

 reference can be brought into coincidence with the lines to be 

 measured. The indications of this instrument are reduced to 

 wave-lengths by means of a series of interpolation curves irom 

 the data obtained by observations of the solar spectrum, the co- 

 ordinates of which are wave-lengths and micrometer readings. 

 The author considers the advantages of the instrument to be 

 (i) great precision in results; and (2) convenience in use. 

 In illustration of the former quality he quotes twenty readings 

 of the point at which there is coincidence of the lenses. They 

 are remarkably concordant, the mean being 8*34, while 

 the two extreme readings are 8 "21 and 8 '41 — Prof. Guth- 

 rie then ■ read a paper on the fundamental water-waves in 

 cylindrical vessels. He stated that many attempts had been 

 made to connect wave-lengths with wave-amplitude, and that 

 the most successful of these were by the brothers Weber, who 

 allowed a column of water to fall into one end of a long trough 

 filled with water ; and they ascertained by means of a stop- 

 watch when the crest of the wave reached the other end. Dr. 

 Guthrie has recently made some experiments on this subject, in 

 which he employed a series of five vessels, varying in diameter 

 from 5*5 to 23-5 inches. The water in each was agitated m 

 the centre by a disc of wood, by which means the vessel was 

 made to give what Dr. Guthrie called its "fundamental note." 

 He counted the number of times the wave rose in the centre in 

 a minute, and he found that amplitude has no influence upon the 

 rate. It should also be observed that the wave effect is not the 

 same as if the field were of infinite extent. The following are 

 the results he obtained :— 



From which he deduced the curious result that a constant 

 quantity (5I7'S) is obtained by multiplying the square root of 

 the diameter by the number of pulsations. The question of 

 depth was also carefully considered, and it was ascertained that 

 the number of waves increases slightly with the depth.— Mr. 

 S. C. Tisley read a paper on a new form of magneto-electric 

 machine. After briefly describing the machines which have 



