April z, 1879] 



NATURE 



523 



always connected with vitreous. He did not see that the 

 fX'esence of magnesia would prove or disprove alteration. He 

 did not think a rock could be vitreous if solidified at a great 

 depth, since it would hardly be able to cool with sufficient 

 rapidity. — The gold-leads of Nova Scotia, by Henry S. Poole, 

 F.G.S., Government Inspector of Mines. The author remarked 

 upon the peculiarity that the gold-leads of Nova Scotia are 

 generally conformable with the beds in which they occur, whence 

 Dr. Sterry Hunt and others have come to the conclu.'-ion that 

 these auriferous quartz veins are interstratified w^ith the argil- 

 laceous rocks of the district. With this view he does not agree. 

 He clas^itied the leads in these groups according to their rela- 

 tions to the containing rocks, and detailed the results of mining- 

 experience in the district, as showing the leads to be true veins 

 by the following characters: — (i) Irregularity of planes of 

 contact between slate and quartz ; (2) The crushed state of the 

 slate on some foot-walls ; {3) Irregularity of mineral contents ; 

 (4) The termination of the leads ; {5) The effects of contemporary 

 dislocations ; (6) The influence of strings and offshoots on the 

 richness of leads. The author further treated of the relative age 

 of the leads and granite, and combated the view that the granites 

 are of metamorphic origin, which he stated to be disproved by a 

 study of the lines of contact. He also noticed the effects of 

 glaciation on the leads, and the occurrence of gold in car- 

 boniferous conglomerate. — On conodonts from the Chazy and 

 Cincinnati groups of the cambro-silurian, and from the Hamil on 

 and Genesee-shale divisions of the devonian, in Canada and 

 the United States, by G. Jennings Hinde, F.G.S. After a 

 sketch of the bibliography of the subject, the author described 

 the occurrence of conodonts. In the Chazy beds they are 

 associated with numerous Leperditue, some trilobites, and 

 gasteropods ; in the Cincinnati group with various fossils ; and 

 in the devonian strata principally with fish-remains ; but there is 

 no clue to their nature from these associated fossils. They 

 possess the sa ne microscopic lamellar structure as the Russian 

 conodonts described by Pander. The various affinities exhibited 

 by the fossil conodonts were discn^sed ; and the author is of 

 opinion that though they most resemble the teeth of myxinoid 

 fishes, their true zoological relationship is very uncertain. The 

 paper concluded with a classification of the conodonts from the 

 above deposits. — On annelid jaws from the cambro-silurian, 

 Silurian, and devonian formations in Canada, and from the 

 lower carboniferous in Scotland, by G. Jennings Hinde, F.G.S. 

 After referring to the very few recorded instances of the dis- 

 covery of any p rtions of the organisms of errant annelids as 

 distinct from their trails and impressions in the rocks, the author 

 noticed the characters of the strata, principally shallow-water 

 deposits, in which the annelid jaws described by him are 

 imbedded. A de cription was given of the principal varieties 

 of form and of the structure of the jaws. They were classified 

 from their resemblance to existing forms under seven genera, 

 five of which are included in the family Eunicea, one in the 

 family Lycoridea, and one among the Glycerea. The author 

 enumerated fifty-five different forms, the greater proportion of 

 which are from the Cincinnati group. 



Meteorological Society, March 19. — Mr. C. Greaves, 

 F.G.S., president, in the chair. — The follo\ving were elected 

 Fellows of the Society : — R. Burniston, W. H. Crawford, J. 

 Davies, The Earl of Derby, H. Dowas, S. Egar, I. S. Hodgson, 

 S. HoUins, T. M. Hopkins, H. Homcastle, C. W. Johnso , E. 

 M. Nelson, and F. Wilkin. — The papers read were : — Dew, 

 mist, and fog, by George Dines, F.M.S. The author has during 

 the last two years made a number of experiments to determine 

 the amount of dew that is deposited on the surface of the earth. 

 The plan adopted was as follows : — Glasses similar to ordinary 

 watch-glasses were procured ; the surface area and the weight of 

 each was a-certainei These glasses were exposed to the open 

 air in the evening, being placed on different substances, viz., 

 on grass, on slate, and on a deal board, the two latter being 

 raised a few inches above the grass. A minimum thermometer 

 was generally placed by the side of each glass. It is only on 

 rare occasions that an amount of dew exceeding the coio inch 

 in depth has been deposited upon the measuring glas-es, and out 

 of 198 observations, in only 3 has that amount been exceeded. 

 Fifty-eight observa'ions give the amount from 0010 to o"oo5 

 inch : 107 from 0-005 to o"OOi inch ; 22 less than 0001 inch ; 

 and 8 observations no dew at all. The author think- it may be 

 fturly assumed that the average annual deposit of dew ujion the 

 surface of the earth falls short of i"5 inch. There are two 

 kinds of mist, the morning and evening ; the morning mist is 



caused by the evaporation from the water and the moist groiuid 

 taking place fa-ter than the vapour is taken away ; the air 

 j becomes saturated, bit this does not .'top the evaporation ; the 

 vapour continues to rise into the air, is there condensed, and 

 forms mist, which gradually spreads over a wider surface. The 

 evening mist is produced as follows : — The c 'Id on the grass 

 caused by radiation lowers the temperature of the air above it ; 

 the invisible vapour of water previously existing in the air is in 

 excess of that which the air can retain w hen the temperature is 

 lowered ; the surplus is condensed, becomes a mist-cloud, aid 

 floats in the air just above the surface of the grass. Taken 

 either separately or combined, the mists appear to the author 

 totally and altogether inadequate to account for those dense fogs 

 which at times overspread large tracts of country. Dense fogs 

 near the earth are often accompanied by a clear sky above, 

 when the sun may be seen reflected from the gilded vanes of 

 our public buildings. After long consideration the author is 

 inclined to attribute these fogs to some cau>e at present tmknown 

 to U-, by which the whole body of the air to some distance 

 above the surface of the earth is cooled down, and, as a conse- 

 quence, part of the vapour in that air is conden-ed and form> 

 what has been called an "earth-cloud." — On the inclination of 

 the axes of cyclones, by the Rev. W. Clement Ley, M.A., 

 F.M.S. The object of this paper is to call attention to the 

 evidences recently afforded by the results of mountain observa- 

 tions to the theory that "the axis of a cyclone inclines back- 

 wards." The author first reviews the state of the question up 

 to the present time, and details his own investigations, chiefly 

 founded upon the movement of cirrus clouds ; he then refers to 

 Prof. Loomis's recent " Contributions to Meteorology," in which 

 is discus-ed the observations at the summits and bases of several 

 high mountains, the results of which fully confirm the theory 

 that the axis of a cyclone inclines backwards. The di- cussion 

 on this paper was adjourned till the next meeting. — Contributions 

 to the meteorology of the Pacific. No. III. Samoan or Navigator 

 Islands, by Robert H. Scott, F.R.S. 



Physical Society, March 22. — Prof. W. G. Adams, presi- 

 dent, in the chair. — New Member, Capt. Hastings R. Lees, 

 R.N. — Capt. Abney, R.E., F.R.S., read a paper on obtaining 

 photographic records of absorption spectra. Absorption spectra 

 have hitherto been recorded by the difficult method of hand- 

 copying ; but the discovery by Capt Abney of a silver salt sensi- 

 tive to all rays in different degrees renders the photographic 

 method available. The records thus obtained are photographs 

 of the spectrum of the naked light of the source and of that of 

 the same li^^ht reduced by insertion of the absorbing material in 

 its track, and these are taken parallel, so that the dark absorp- 

 tion lines can be readily compared. Examples of these were 

 thrown by him on the screen. This method can be used as a new 

 weapon in attacking solar physics and determining whether or 

 not compound bodies exist in the sun. Absorption spectra to 

 compare with the sun can be got for compound bodies by burning 

 the matter in question in a flame in front of the slit and passing 

 a bright light through the flame. — Prof. Guthrie, F,R,S., then 

 read a paper on the fracture of colloids, as illustrated by experi- 

 ments on the breakage of glass plates either by pressure or heating 

 at the centre or round the circumference. Circular plates of 

 glass, pressed at centre or circumference, break in radial lines. 

 However supported, a plate breaks in the same fashion if heated 

 in the same way. If heated in the middle the crack is peak- 

 shaped, like an obelisk on a double pedestal, two cracks forming 

 the outline, with sometimes a third down the middle. The two 

 cracks unite before they reach the fA^& on one side, and (as 

 afterwards pointed out by Prof. W. G. Adams) the three ex- 

 tremities of the two cracks all meet at right angles to the edge. The 

 crack age varies with the size and shape of the plates, the flame, 

 and kind of glass ; but the type is the same for all. Cracks cross 

 each other. Prof. Guthrie defined a crack as the line where 

 the ratio of cohesion to strain is lea-t, and likened it to the 

 lightning flash, Mr. W. Chandler Roberts, F.R.S., said that 

 he had observed once a volute spiral crack in dried hydrated 

 silicic acid, and recommended Prof. Guthrie to study cracks in 

 agate, which is the most perfect colloid known. 



Geneva 



Society of Physics and Natural History, Noyember 6, 

 1878. — M. Raoul Pictet read a paper on temperature and on the 

 general synthesis of all calorific phenomena. The purpose of this 

 research is to prove the absence of rigorous definition of the 

 word "temperature," \ht petitio principii on which the construe- 



