30 



NATURE 



[November 14, 1895 



fore Wiener's law is not true of this zone taken apart. If we 

 subtract the sun-heat received in this zone where glacial con- 

 ditions never existed, we shall find that the proportions in the 

 temperate and polar zones combined are not 63 to 37, but 38 to 

 12. So that Wiener's law is not true of these zones where 

 glacial conditions alone existed. If, instead of taking the tropics, 

 we take the area limited by the parallels of 45°, which is a better 

 boundary for the district displaying glacial phenomena, the dis- 

 parity is still greater. At Edinburgh, as CroU long ago said, the 

 proportions are about 3 to i. Does Mr. Hobson dispute this ? 



(4) Dr. Ball nowhere connects Wiener's law as a cause with 

 the Glacial age as an effect by proof of any kind. He merely 

 offers us certain obiter dicta, and argues that if the present pro- 

 portions of sun-heat were distributed over a winter of 199 days 

 and a summer of 166 days, we should have a glacial climate in 

 Britain. Since the proportions of sun-heat actually recorded in 

 Britain at this moment in our 199 coldest and 166 warmest days 

 respectively show a far greater disparity than that represented 

 by these figures, I may, I think, ask if Mr. Hobson admits this 

 reductio ad absiirdum of Sir Robert Ball's argument to be valid? 



(5) Lastly. For the first time, Mr. Culverwell has applied 

 numerical tests and methods to the problem of discovering the 

 actual and not the hypothetical results on climate caused by a 

 varying eccentricity of the earth's orbit. He has done so by 

 comparing the actual sun-heat received by each latitude now, 

 and contrasting it with the actual sun-heat received by the same 

 latitude in the time of greatest eccentricity, and has shown that 

 the limits of variation do not amount to more than can be 

 measured by removing a parallel of latitude from 3^ to 4 degrees. 

 This to some of us is absolutely conclusive, not only against Dr. 

 Ball's arguments, but against all astronomical theories, including 

 Croll's. 



The real point and meaning of my letters is that in regard to 

 the astronomical theory of an Ice age all the kind of reasoning 

 employed by Sir R. Ball and its consequences are fallacious. 

 They have been swept away and shown to be worthless by Mr. 

 Culverwell's method of solving the problem, which is inductive 

 and decisive, and which rigorously proves that Sir Robert Ball's 

 results are as extravagantly baseless as his method is unfruitful. 

 This being so, it is most clearly incumbent upon the Lowndean 

 Professor either to answer his accomplished critic or to withdraw 

 his book, which is only misleading the unwary by having its 

 mistaken and shattered arguments sheltered under the Astro- 

 nomical Chair at Cambridge. It ought certainly to have no 

 place in a series entitled " Modern Science," where ascertained 

 results and not ingenious fallacies ought to find a place. Nor 

 ought Mr. Kegan Paul's name to appear on its title-page as a 

 guarantee of its scientific soundness. 



The Athenjeum Club, October 29. Henry H. Howorth. 



Curious Aerial or Subterranean Sounds. 



Prof. G. H. Darwin, in Nature for October 31, p. 650, 

 asks for information as to the " Barisal guns." The name is 

 derived from Barisal or Burrisal, a town in the eastern part of 

 the Gangetic delta, and the best and most recent account of the 

 sounds known as the " Barisal guns" is to be found in the report 

 of a sub-committee of the Asiatic Society of Bengal, published 

 in the Proceedings of that Society for 1889, p. 199. 



The great difficulty in the way of accepting the suggestions 

 of iSIessrs. Meldola and Davison (Nature, November 7, p. 4), 

 that earthquake shocks are the cause of the sounds, is the re- 

 striction of the " Barisal Guns," so far as is known, to a com- 

 paratively small area, where earthquakes are of rare occurrence, 

 and to a particular season of the year. 



W. T. Blanford. 



{Translated by Prof. G. H. Da7-win.'\ 



An article, by Prof. G. H. 'Darwin, on " Barisal Guns and 

 -Mistpouffers " appeared in Nature for October 31. Sum- 

 marising a letter in which I drew his attention to this phenomenon, 

 he mentions two sources for these mysterious sounds, which my 

 friend M. Rutot and I have considered as possible, namely that 

 the origin is entirely terrestrial, or that it is a special phenomenon 

 of atmospheric electricity. It is as well, perhaps, also to point 

 out another purely atmospheric source, viz. that it may arise from 

 thef abrupt displacement of a mass of superheated air in unstable 

 equilibrium, which rises suddenly in the atmosphere. 



This was the explanation given to M. Lancaster by the late 



NO. 1359. VOL. 53] 



M. Houzeau, the astronomer, on the former sending him my 

 first notes on this phenomenon, in about 1881. M. Houzeau also 

 stated that he had himself observed the noises, but that he could 

 not suggest any more plausible explanation than the above. 



In confirmation of this hypothesis, I would remark that this 

 year the mysterious detonations were heard up to the end of 

 September, and even up to the beginning of October, not only by 

 me but by several of my friends and correspondents ; this is much 

 later in the year than usual. Now great and unusual heat pre- 

 vailed this year during the whole autumn, and this coincidence 

 affords a strong support to the theory of an origin arising from 

 certain conditions of rise of temperatyre. 



Sailors of the port of Ostend assert that " Mistpouflfers" 

 prevail over the whole of the North Sea as far as Iceland, and 

 they consider them to be a sign of fine weather, with calms 

 and heat. 



The mysterious noises, mentioned to me by Mr. Clement 

 Reid, which are heard on Dartmoor and in Scotland near the 

 Highland Fault, are not perhaps exactly comparable with 

 "Mistpouffers" ; for Mr. Reid writes to me that these sounds 

 are probably associated with those incessant tremors of the 

 earth's crust, which are well known in these districts. With 

 respect to sounds of this peculiar kind, readers of Nature will 

 find an interesting note by Mr. Charles Davison, entitled " On 

 Earthquake Sounds," in the Geological Magazine for May 1892. 



I might add many interesting data concerning " Mistpouffers," 

 but I have promised to reserve them for the Belgian magazine 

 Ciel et Terre, edited by M. Lancaster. In that journal, the 

 readers of Nature who are interested in this subject, will 

 shortly find a complete account of the papers which have come 

 to my knowledge ; to which they will doubtless be able to add a 

 number of facts and observations, which will prove of great 

 service for the scientific study of the question. 



Ernest Van den Broeck. 



39 Place de I'lndustrie, Brussels. 



I have heard many queer noises in lonely spots, and wish I 

 had made note of the time and place and circumstances. But 

 though I have few exact facts and figures, I have a very distinct 

 recollection of many such observations, some of which are a direct 

 answer to the question asked by Prof Darwin in your number of 

 October 31, while others seem to have a bearing upon it. 



I have sometimes heard on the mountains north of the great 

 Craven Faults, from which I looked over low ground towards 

 Morecambe Bay, what I always took to be the sound of heavy 

 guns somewhere out seaward. They were not, however, repeated 

 at such intervals, nor for so long a time as to support the view 

 that it was the sound of artillery practice ; and, when I made 

 inquiries from friends who resided in the district, I never learned 

 that there was anything of the sort going on. The sound struck 

 me as peculiar, but I could not find any satisfactory explanation 

 of it. I considered many possibilities. First, there was the 

 general question of the different transmission of such sounds 

 according to the state of the atmosphere. Fog, for instance, 

 affects it. In the particular case I have mentioned, I knew 

 there were great quarries in various places within a few miles, 

 and I had always before me the possibility of my having heard 

 the sound of blasting echoed by some combination of cliffs to 

 where I was. 



The noises I heard were just such as are produced by the thud 

 of the wave as it fills a cave. The muflSed sound of the impact of 

 water is heard a long way off. An idea of its force may be gained 

 from cases in which the air, instead of being compressed in the 

 hollow of the rock, finds an opening to the surface of the ground 

 above, and rushes out, sometimes followed by a spout of spray. 

 Its recurrence is irregular, and it lasts only for the short time 

 when the rise and fall of the waves just fills and empties the 

 cave. The direction of the transm'ssion of this sound to long 

 distances is still more uncertain. 



In the case of the air-thuds on the Yorkshire Fells this ex- 

 planation is extremely improbable, and the "guns of Barisal," 

 so named from the town and river of that name, boom across 

 the flat delta of the Ganges, where there can be no cliffs or 

 caves. What is really common to the two areas suggests 

 another possible explanation. 



The sound of the first blow of the curled wave upon the shore 

 or on the sea, and of the outburst of the great volume of air in- 

 cluded in its fold, is carried an immense distance. I have heard 

 it much resemble heavy guns. It is exceptional and irregularly 

 intermittent. It is only when the tide has reached one part of 



