December 7, 1899] 



NA TURE 



127 



in the British Museum," a large part of which was written 

 by Dr. Sharpe, but the new species described since the 

 pubhcation of the twenty-seven volumes which comprise 

 the " catalogue " are here included. Proofs of the work 

 have been read and corrected by a number of leading 

 ornithologists throughout the world, assistance sufficient, 

 as Dr. Sharpe says, to give the work " the importance of 

 an international publication." 

 Human Nature: its Principles and the Principles of 



Physiognomy. By Physicist. Part ii. Pp. viii + 175. 



(London : J. and A. Churchill, 1899.) 

 The nature of the volume can be indicated by stating 

 one of the propositions of the author's theory of colour : 

 "That exhausted viable matter absorbs the luminous 

 rays, and reflects the invisible (potential) rays, therefore 

 it is dark or nearly colourless, sometimes violet or purple 

 ijeing perceptible ; and that viable matter stored with 

 energy reflects the luminous rays, therefore it is yellow 

 or some colour containing excess of yellow, as brown, or 

 cream colour, »S:c., and absorbs the invisible or potential 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications. \ 



The Cause of the Darjeeling Landslips. 



Prof. John Milne's prompt contradiction in the Times of 

 October 3, and in Nature (5th) of the telegraphic statement 

 concerning the cause of the recent Darjeeling landslips is a dis- 

 tinct " score " for the seismograph. With the Committee ap- 

 pointed by the Bengal Government to investigate the causes of 

 the recent disaster, and to formulate measures for anticipating 

 its possible recurrence, I made special inquiries into the alleged 

 occurrence of earthquakes at Darjeeling on the night of 

 September 24-25, and we all agreed that there was no evi- 

 dence to show that any seismic phenomena whatever occurred. 

 No movements were felt in well-built houses, and those that were 

 noticed, as well as the sounds which were heard during the 

 violent cyclone, were only of a kind that might be expected in 

 the ill-built, rickety structures which, for the shelter of those 

 who temporarily reside in our hill stations, are knov/n to their 

 •owners as " houses." Local earth-tremors may have resulted 

 from the slips, but they were the effects, not the cause, of the 

 latter. 



The unprecedented rain which accompanied the September 

 cyclone was a sufficient and satisfactory immediate cause for the 

 numerous landslips near and in Darjeeling. Up to the morning 

 of the 23rd, the monsoon rains measured some 17 inches in 

 excess of the average for previous years, and the thick soil-cap 

 was consequently already saturated. The cyclonic depression first 

 reported by the Meteorological Department to be formed to the 

 south-east of False Point in the Bay of Bengal moved northwards 

 until its centre, on the 24th, had reached lat. 25°, causing heavy 

 rain over most of the province. During the twenty-four hours 

 ending at 8 a.m. on the 23rd, 5 "31 inches of rain fell at Dar- 

 jeeling, followed by 19*40 inches during the next twenty-four 

 hours. Of the latter amount 1432 inches fell between 4 p.m. 

 on the 23rd and 4 a.m. on the 24th, being thus over an inch an 

 hour for a stretch of twelve hours. It was during this last 

 period, when the rainfall was at its heaviest, that the disastrous 

 slips occurred. 



The hill-sides in the neighbourhood of Darjeeling are by 

 natural means already at or near their angle of repose for earth- 

 slopes, and the reduction of frictional stability, due to the 

 thorough saturation by the heavy rainfall of September 23-24, 

 was sufficient to permit slipping of the less stable portions 

 of the soil-cap. The biotile-gneiss massif below is undisturbed 

 and perfectly stable : there is nothing here comparable to Naini 

 Tal, where the slates, by differential movement along their bed- 

 ding planes, have caused cracks in the masonry structures built 

 •upon them. In Darjeeling the slips were confined entirely to 

 ithe soil-cap, which ran down the steep hill-sides as rivers of mud, 



NO. I 57 I, VOL. 61] 



and, with occasional included boulders, bombarded the back 

 quarters of some of the houses. A more interesting example on 

 the eastern side of the Jalapahar ridge shows movement on a 

 comparatively large scale now in progress. The sides of the 

 moving mass are defined by longitudinal shear cracks, whilst its 

 upper region — the Abrissgehiet of Heim— shows gaping fissures 

 with, in the uppermost ones, a vertical displacement of about 

 8 feet. A description of this interesting landslip, with map and 

 photographs, will be issued at a later date by the Geolc^cal 

 Survey Department. T. II. Holland, 



Geological Survey of India, Calcutta, November 8. 



Barisal Guns. 



I MUST first state how I came to notice this phenomenon so 

 well known in Bengal. Early in February, 1890, I was posted 

 to Backergunge, as District Superintendent of Police, and re- 

 mained there till December, 1891, a period of twenty-two 

 months. In order to travel quickly over the district a steam 

 launch was always at my service, and as I had to visit each of 

 the num erous police stations scattered all over the district at 

 least twice every year, there are few places in Backergunge I 

 have not visited repeatedly. 



Shortly after my arrival I received a letter from my friend, 

 Mr. G. A. J. Rothney, of the firm of Messrs. John Dickinson 

 and Co., 65, Old Bailey, who has a very wide experience of 

 India, and takes a keen interest in natural phenomena, asking 

 me to try and elucidate this phenomenon of the Barisal Guns ; 

 to make careful observations and record them on the spot. 

 This I did, and I now forward a copy of the note I sent him. 



The causes usually assigned for this phenomenon are three in 

 number, viz. : — 



(i) High banks of rivers falling in ; 



(2) Surf breaking on the shore, and 



(3) Subterranean explosions. 



The first of these theories cannot stand in face of the undis- 

 puted fact that any such sound would be purely local and could 

 be heard only at very short distances, whereas it is admitted 

 these guns are heard at places a hundred miles apart. The 

 second is equally untenable when we remember the whole 

 delta is composed of alluvial deposit, without a rock for hundreds 

 of miles. And, thirdly, this alluvial deposit entirely does away 

 with the possibility of subterranean explosions. 



It is well known to all navigators of these waters there is a 

 peculiarly deep depression to the south of this delta, which 

 either has never been sounded, or, if sounded, has shown a 

 most unaccountable depth, and it is assumed these reports 

 emanate from this depression. But I am not inclined to accept 

 this as a sufficient explanation, as the sounds are so very 

 irregular in their frequency. We all know that Geysers in 

 various quarters of the globe are celebrated for shooting out 

 great masses of water from time to time ; but these usually have 

 some periodicity, and their times for discharge have been, more 

 or less, tested and reduced to some well-known law or theory. 

 Now the very irregularity of the Barisal Guns proves they can 

 be subject to no such law, for, if they were, the phenomenon 

 should be heard with some regularity, whereas, as I have shown 

 in my note to my friend, their irregularity is one of their most 

 noticeable features.- 



There are two special occasions to which I would draw 

 attention : the first in February, 189 1, when from the southern- 

 most outpost, Chaltabuni, I followed the reports for some forty 

 miles out to sea ; the second, mentioned in my letter to the 

 Surveyor-General of Bengal, when, in August, 1891, for more 

 than six hours, I followed the reports without getting any 

 appreciably nearer, and also never hearing them to the north 

 of me. Henry S. Schurr. 



34, Bloomsbury Street, W.C, November 28. 



{Report.) 



Barisal Guns are heard over a wide range extending from 

 the Twenty-four Pergunnahs through Khulna, Backergunge and 

 Noakhali, and along the banks of the Megna to Naraingunge 

 and Dacca. They are heard most clearly and frequently in the 

 Backergunge district, from whose headquarters they take their 

 name. 



These Guns are heard most frequently from February to 

 October, and seldom in November, December or January. One 

 very noticeable feature is their absence during fine weather, 

 and they are only heard just before, during, or immediately 

 after heavy rain. 



