June 19, 1879] 



NATURE 



169 



Has any one, in the discussion of Mallet's hypothesis, thought 

 of bringing its probability to such a test as the volatilisation of 

 the hydrocarbons of coal-beds in a highly plicated region like 

 Belgium ? 



It is a remarkable fact, and one which seems to me inconsistent 

 with the mechanical theory of eai-th-heat, that of two extensive 

 regions, Belgium and Eastern Pennsylvania, equally and exces- 

 sively disturbed by complications, all the coal-beds of the one 

 are anthracite, and all those of the other are bituminous. 



Again, of two regions equally undisturbed, Western Penn- 

 sylvania and Arkansas, the horizontal coal-beds of the one are 

 bituminous and of the other anthracite. 



Surely, if movements of stratum on stratum produce all the 

 needful heat, no plicated coal-beds should escape being converted 

 to anthracite ; and I should much like to hear from English 

 geologists how this argument is to be met. My own explanation 

 of the origin of anthracite is not worth much, but it is the best 

 I know. I refer such origin to three causes acting in conjunc- 

 tion — (i) Heat due to superposed (now whoUy or partially re- 

 moved) Permian and later formations ; (2) Greater proportion 

 of sands in the anthracite and of clays in the bituminous coal- 

 measures ; and (3) Plication and fracture, permitting the exit of 

 volatilised hydrocarbons into the atmosphere. 



American Philosophical Society, J. P. Lesley 



Philadelphia, May 22 



Evolution Old and New 



Mr. a. R. Wallace writes, in Nature, vol. xx. p. 143, 

 that, according to the theory which I support, Australian (and 

 more especially Queensland) sheep should show a tendency to 

 grow a scantier and thinner fleece than theu: English ancestors. 

 "If Mr. Butler," he continues, "could adduce on good autho- 

 rity such a fact as this, he would have some evidence in his 

 favour, instead of which he can only make suppositions." 



I never was in Australia, but had some years' experience of 

 sheep-farming in New Zealand. It was generally believed, in 

 my time, that fleeces soon became short and hairy in Queensland, 

 and even in the more northern part of New South Wales. You 

 must, however, have many readers who could tell us what the 

 facts are. May I hope that you will kindly insert this, so as to 

 get the matter settled by eliciting information from a competent 

 authority ? I am speaking, of course, of sheep that are left to 

 the effect of the climate, without being frequently crossed with 

 rams from colder countries. Do the fleeces of such sheep dete- 

 riorate in Queensland ? S. Butler 



June 12 



The River Elbe 



In Nature, vol. xiv. p. 498, some particulars are given of 

 measurements made in 1871 and 1872 of the water flowing past 

 in the Elbe at the boundary between Saxony and Bohemia. 

 The river basin in Bohemia above this point is stated at 880 

 square miles, which is evidently wrong, as the annual discharge 

 of 6,179, coo,ooo cubic metres(2i8,223,743,ooo cubic feet) would 

 give a depth of 107-64 inches run off the ground. Measuring 

 roughly on the map, the area of Bohemia — which, apparently, 

 all drains into the Elbe— is 20,000 English square miles. If, on 

 the other hand, the measurements of the river water and the 

 solids in solution and suspension are correctly given, and the 

 river basin is 20,000 square miles, the rainfall must have been 

 exceptionally low at the time the measurements were taken, as 

 the figures represent only about half that of the mean annual 

 flow off the ground in the Danube basin, which is 9'o6 inches. 

 Perhaps the writer of the notice will be able to find out how 

 these discrepancies occur. I may add that, taking the figures 

 as given m Nature, 607 tons per square mile per annum are 



i removed in solution in the Elbe water. From a district com- 

 posed mostly of Silurian rocks, this is manifestly absurd. Ac- 



( cordmg to my calculations,! 727 tons per square mile are annu- 



' ally removed in solution in the Danube water. 



. Blundellsands, June 17 T. Mellard Reade 



Electric Light 



In Nature, vol. xx. p. no, an account is given of Sir 

 William Thomson's evidence on the electric light. It is stated 

 "that one horse-power had produced 1,200 candles of actual 



' " Geological Time," Proceedings of Liverpool Geological Society, Session 

 1070-7. 



visible electric light, whereas one horse-power of energy would 

 only produce I2candle gas-light." In the report of Sir J. W. 

 Bazalgette and Mr. Keates to the Board of Works, which is 

 probably the best report we have yet had on the subject, as to 

 the actual cost of the electric light on the Thames Embankment, 

 it is stated that the cost of the electric light was S7S(i'. per hour, 

 whereas the cost of the gas required to produce a light equal to 

 the electric light as regards illuminating power, in an opal globe, 

 was 2-ood., and in a frosted globe 3'50fl'. per hour. Would 

 any of your numerous readers be kind enough to give me some 

 idea of the qualifications to be appended to the above state- 

 ments, which will reduce the long odds calculated by Thomson 

 of 100 to I in favour of the electric light, to the odds of 2 to I 

 against it as found in actual practice? In conclusion may I 

 venture humbly to suggest that such conflicting statements as 

 the above, if unexplained, are apt to bring the dicta of scientific 

 men into disrepute with the tliinking portion of the general 

 public. F. J. M. P. 



The Climbing Perch 



The aquarium of the Zoological Society's Gardens in Regent's 

 Park has lately received a contribution of five specimens of the 

 "Climbing Perch" (Anabas scandens). They were very kindly 

 obtained for me by my friend, Mr. A. Ferguson, of Colombo, 

 Ceylon, and were brought home in excellent condition by my 

 brother, Mr. A. F. Dobson. Mr. Ferguson (who is so well 

 known in Ceylon as a naturalist of great experience) kept the 

 fish for some months in an aquarium, and trained them to take 

 chopped meat from the hand, so that they were in the best 

 possible condition for their long journey. 



The first specimens of this fish which arrived alive in Europe 

 were sent by me from Calcutta in 1872 to the Royal Zoological 

 Gardens in the Phcenix Park in Dublin, where they lived for a 

 considerable time. 



I have described (P. Z. S., 1874), in my paper "On the 

 Respiration of Indian Fresh-water Fishes," the manner in 

 which Anabas scatidens takes in, and rejects again, the atmo- 

 spheric air, and on a visit to the aquarium in 'the Gardens the 

 peculiar conduct of these fishes when respiring may be witnessed 

 by any one. 



Mr. Ferguson informs me that he has specimens of some 

 species of Ophiocephali and the remarkable Arms bakeri, which 

 carries its young in its mouth, in training, and I hope soon to 

 have an opportunity of having them safely carried to England. 



Netley, June 14 G. E. DoBsoN 



Oxygenated Rain 



On Thursday, June 12, at half-past eleven in the morning, a 

 remarkable shower of rain fell over London, which might almost 

 be described as "effervescing ;" the drops whilst falling appeared 

 to be colourless and perfectly transparent, but on striking against 

 any solid surface they became milky, and 'on close examination 

 it was evident that this cloudy appearance was caused by a 

 number of very minute air-bubbles, which rapidly increased in 

 size, and then burst. From the bleaching power which this rain 

 appeared to have, I am led to believe that there was nascent 

 oxygen in the gas thus evolved. Those who traverse the streets 

 of London in the early morning may now and then observe the 

 red colour of all bright iron- work in the pavement, such as coal- 

 plates, &c., due to the oxidising influence of a thunder-shower 

 in the night ; this effect does not follow every thunder-shower, 

 but seems to indicate a peculiar atmospheric condition. Have 

 any memoranda on this subject been recorded ? 



Edward Solly 



WILLIAM FROUDE-' 

 T AST week we called attention to Mr. Froude's dis- 

 ■•-' coveries of those laws of motion of floating bodies, 

 upon which the behaviour and safety of a ship passively 

 floating among sea waves depends. We now purpose 

 giving a brief outline of his researches in another branch 

 of hydrodynamics by which he arrived at a true apprecia- 

 tion of the nature and amount of the resistance opposed 

 by water to the passage of a body like a ship through it. 

 In connection with the resistance of ships, the subject of 

 marine propulsion, which Mr. Froude has also done much 



' Continued from p. 150 



