Jan. 6, 1881] 



NA TURE 



219 



Paflas, fAkap, Abors, Mishmis, Singphu?, [and Nagas (all) confined to Itill races, and not seen in | lain races; that the 



build pile-dwellings, as do the Kamtis. " invariable explanation offered to inquiry is that on the hill tops 



Several peculiarities are noteworthy, i.e. that the custom is | and jpnrs, where alom the villages are built, there is very little 



level land; also that this form of hou e is a necefsity among 

 races that keep pigs and goats, which to any casual visitor is at 

 once obvious. 



As it is possible that this question may afford unexpected 

 results when examined, I inclose sketch of a Naga " Morang," 



or skull hoii?e, uhich with its platform is the same as those they 

 live in. Different tribes have variations of ihe pattern, and 

 most have the platform balcony in some shape or other, and the 

 posts go through the roof in some Nagas houses alone. 

 Asam S. E. Peal 



Landslips. — The Cheshire Subsidences 



Under the guidance of Mr. Thos. Higgin, F.L.S., and your 

 correspondent Mr. Ward, I have just been examining the subsi- 

 dences that have been lately taking place in the neighbourhood 

 of Northwich. To understand how they occur, it is necessary 

 to know that there are two beds of rock salt in the Triassic 

 marl. The upper bed, 25 yards thick, is from 40 to 60 yards 

 below the surface ; the lower, 35 yards thick, is separated from 

 the upper by about 10 yards of hard marl. The greater bulk of 

 the salt is obtained in the form of brine pumped up from the 

 upper bed. The lower bed is to a smaller extent worked as a 

 salt-mine. From these operations two classes of subsidences 

 result : the one general and gradual, due to the removal in solu- 

 tion of the rock salt of the upper bed by percolation of water 

 and pumping, by which the surface of the ground sinks in undu- 

 lations ; the other, sudden fallings in of the ground into the 

 mines, forming crater-like pit*. It is to these I wish 10 call 

 attention. I was fortunate enough to see one before it had 

 become, as they all do, partially filled with water. I should 

 judge it to be about 70 feet deep, 150 feet diameter at the top, 

 and 20 or 30 feet at ihe bottom, where a little water was kdging. 

 The problem to account for is how such an inverted cone of 

 marl capped with boulder-clay and drift-sand could apparently 

 have disappeared through so small a hole? The explanation 

 appears to be this : By percolation of water the roof of the mine 

 begins locally to give way and fall into the mine, gradually 

 working its way to the surface, where it fir.t appears in the form 

 of a hole about the size of a well. The vacuity will no doubt 

 take a conical form, the base being at the roof of the mine ; 

 once the hole is formed, the surface ground begins to slip and 

 fall in around, gradually ei larging the orifice, the material dis- 

 appearing into the mine below. This continues until the bottom 

 is filled up and the sides of the "crater" attain the angle of 

 repose. The whole thing will occur in a night. The subsidences 

 certainly present a very remarkable appearance from the 'regu- 

 larity of their circular or elliptical form and funnel crater-like 

 shape. It is evident such subsidences could not happen except 

 under special conditions, such as are provided by salt-mining 

 and pumping in these Keuper marls. T. Mf.ll.\rd Keade 



Park Corner, Blundellsands, Liverpool, December 22, 1880 



Animal Reasoning 



I SEND an account of a singular act of animal intelligence 

 which may not be uninteresting to the readers of Nature. A 

 lady, a friend of mine, was at one time matron of a hospital for 

 poor women and children which was maintained by subscription. 

 One of the inmates was a 1 lind girl who was there not as a 

 patient, but temporally till a home could be found for her. She 

 had learned to feed herself, and at meal times a tray containing 

 her dinner was placed on her knees as she sat in a comfortable 

 chair for her special convenience in feeding herself. One day 

 while she was eaung, the pet cat of the establishment placed 

 herself before the girl and looked long and earnestly at her, so 

 earnestly that the matron, fearing the animal meditated some 

 mischief to the girl, took her out of the room. Again the next 

 next day, at the same hour, the cat entered the room, but this 

 time walked quietly to the girl's side, re.ared herself on her hind 

 legs, and noiselessly, stealthily reached out her paw to the plate, 

 selec ed and seized a morsel that pleased her, and, silently as she 

 came, departed to enjoy her stolen meal. The girl never noticed 

 her loss, and when told of it by her companions laughed very 

 heartily. 



It is evident that the cat from observation had entirely satisfied 

 herself that the girl could not see, and by a process of reasoning 

 decided she could steal a good dinner by this practical use of her 

 knowledge. K' ?■ 



Cambridge, Massachusetts 



Ozone 



The letter of J. P. on this subject hardly gives enough d.ata to 

 enable one to found an opinion upon ; but is it not possible the 

 paper is coloured by ozone from the air? It is well known that .a 

 flame is the most potent method of collecting atmospheric elec- 

 tiicity, anda properly-irsulated spirit flame ignited indry air seldom 

 fails to show some traces. I would suq:aest the experiment being 

 repeated on the exposed plate of a gold leaf electrometer, the sur- 

 rounding conditions of place, sir, &c., being noted : also under 

 a bell glass, where such condiiions would be varied. Ozone is 

 very strong just now, my paper this morning reaching 10, the 

 limit of Negretti and Zambra's scale. J. Rand Capron 



Guildowr, December 28, 1 880 



