Dec. 1 6, iSSo] 



NA TURE 



M5 



making the brook from 30 to 40 feet wide instead of 20 as at 

 first. 



Tlie quantity of water thus rushing down for twelve liours from 

 the commencement would be fully 600,000 tons. The water in 

 one direction over a surface of 160 acres was lowered one foot in 

 the space of three hours. Shortly after this water commenced 

 to ru!.h below it made its way through a weak portion of a barrier 

 wall into a rock salt mine that was being worked. This mine, 

 extending over fifteen acres, and having a worked-out depth of 

 eighteen feet, was completely filled and all the tools, materials, 

 waggons, tram\\ays, &c., entirely lost. It will be quite im- 

 possible ever to pump out the water. Besides this mine, all the 

 old abandoned mines were filled, and the briue, which stood at 

 100 yards from the surface on the Sunday, stood at 24 yards on 

 IMonday night. The water being fresh, great damage was 

 expected by the solution of the salt. This soon occurred, for an 

 old mine that fell in forty-two years ago, and the cavity of which 

 had been filled v/ith water, gave way, and suddenly the M'hole 

 land over a circle of about 500 feet in diameter sank, and a large 

 portion of water escaped into neighboming pits. The ground 

 cracked and rifted and subsided, and a length of road of 160 

 yards was destroyed, as also pipes conveying brine to the salt 

 works. A large reservoir holding brine was split across and all 

 the brine let out ; the rending of the earth passed through two 

 kilns of bricks, dropping one-half of the kilns at le.ast 2 feet. On 

 the Monday afternoon a tall chimney 90 feet in height became 

 affected, and in a few hours fell w ith a great crash. The air that 

 had filled the cavities below was forced out by the inrush of 

 water, and caused all the pits and brooks near to bubble and boil 

 violently, ■»> hilst in some of the rifts where water occurred minia- 

 ture mud geysirs were formed, throwing up mud 10 or 12 feet 

 high. These appearances extended over a district between two 

 brooks for the space of 2000 feet. On Wednesday night a large 

 hole 30 yards in diameter and 30 yards deep fell in, and more 

 subsidences are daily expected, as the fresh v^ater will eat aw'ay 

 the pillars supporting the roofs of the abandoned mines. 



The cavity formed on Monday is full of AAater, and the brook 

 now runs through it. Some idea may be firmed of it Avhen I 

 mention that it is crater-like, and of about 200 feet in diameter. 

 On sounding it on Wednesday I found a depth of 78 feet of 

 water in the centre, and various depths from 70 to 60, 50, and 

 so on to about 12 feet at the margin. On Sunday, on the spot 

 which is now 78 feet, there ^vas a sandbank with ils surface 

 above the water. 



Serious injury has been done to one set of salt works, and five 

 sets are stopped for want of brine, the pipes being broken and 

 the road destroyed. 



As the salt trade increases these enormous sinkings keep in- 

 creasing, and become more alarming in their character. 



Erookfield House, Northwich Thos. Ward 



The Geology of East-Central Africa and the Subterra- 

 nean Forest in Bombay 



In Mr. J. Thomson's very interesting " Notes on the Geology 

 of East-Central Africa" (Nature, vol. xxiii. p. 104) he re- 

 marks tlmt doubtless the immense development of volcanic rocks 

 described by myself (and I may add by several previous ex- 

 plorers) in Abyssinia is of the same age as the volcanic rocks at 

 the Cape of Good Hope, assigned to tlie Trias. 



Mr. Thomson has, I think, overlooked the circumstance that 

 whatever may be the age of the Cape volcanic rocks, the teaks of 

 Abyssinia cannot be older than Jurassic. As I have shown [Quart. 

 Jour. Geo!. Soc, 1S69, pp. 403, &c,, and " Geology and Zoology 

 of Abyssinia," pp. 184, &c.), there are in the Abyssinian high- 

 lands two groups of bedded dolerites and trachytes, the upper 

 of which rests unconformably on the lower, while the latter 

 overlies limestone with Jurassic (Middle Jurassic) fossils. 



I trust that Mr. Thomson will pardon my suggesting the possi- 

 bility of the Tanganyika sandstones being river valley deposits, 

 like the Gondwana series of India, rather than lacustrine. I 

 may be mistaken, but the description appears to me to indicate 

 beds coarser than those usually deposited in an extensive lake 

 basin. 



In the same number of Nature, p. loj, is a brief notice of a 

 " Subterranean Forest in India." As I understand the account 

 given, the forest should perhaps rather be termed submarine than 

 subterranean. My object in calling attention to this notice how- 

 ever is to point out that a previous description of the same 

 formation was published in the Kirords of the Geological Sui-vey 



of India for 1S7S, vol. xi. p. 302. This account is by Mr. G. 

 E. Ormiston, Resident Engineer, and agrees in all essential 

 particulars with the note in Nature. I appended a few remarks 

 on the geological bearing of the discovery. Tiie "forest" has 

 clearly been depressed, whilst neighbouring tracts in Bombay 

 island appear to have been elevated in comparatively recent times. 



W. T. Elan FORD 



Dr. Siemens's Gas-Grate 



Having endeavoured for some years past to heat my study by 

 gas appliances, and having utterly failed in obtaining a comfort- 

 able temperature of 60°, as a last effort to accomplish my object 

 I had fitted into an ordinary grate Dr. Siemens's arrangement of 

 copper and iron, the construction of which was communicated 

 to the public in the pages of Nature, vol. xxiii. p. 25. Before 

 giving the results of the trial of Dr. Siemens's gas-grate I may 

 mention in what way my former gas-stoves failed. My first gas- 

 fire consisted of gas and asbestos, but this gave out fumes which 

 were quite intolerable ; my second trial i\as with a gas-stove re- 

 flecting heat from a copper lining ; this not only failed to warm the 

 room, but was a cheerless and grim apology for a fire, and to obtain 

 even a moderate degree of temperature a constant and expensive 

 consumption of gas was necessary. With Dr. Siemens's gas- 

 grate all that is required to produce a good cheerful fire radiating 

 heat to all parts of the room, and maintaining a temperature 

 from 60° to 62°, is to turn on the gas full for about twenty 

 minutes, and as soon as the Ijwer stratum of coke becomes 

 incandescent, the gas may be quite turned off, the fuel, whether 

 coke or anthracite, continuing to burn for five or six hours 

 without any further expenditure of either gas or fuel. 



If the fire is required for a longer time, or if at any time a 

 more rapid combustion is wanted, it is only necessary to turn on 

 the gas again for a few minutes and add more fuel. This is my 

 experience of Dr. Siemens's gas-grate, and I^consider it a great 

 boon to householders who desire well-warmed rooms combined 

 with economy. After the lucid description of the gas-grate 

 given by Dr. Siemens in Nature, it would be piresumption in 

 me to discuss the scientific explanation of its action ; I shall 

 only, in conclusion, venture to claim for it the following advan- 

 tages which I believe it to possess over every other kind of gas- 

 stove yet invented : — 



1. It gives a clear, smokeles?, cheerful fire. 



2. It is most economical, and very soon pays the cost of the 

 construction. 



3. Being absolutely smokeless, contributes nothing to that 

 constituent of our London fogs which renders them injurious in 

 so many ways. 



This last advantage, if multiplied by every householder at an 

 outlay of 25^., adopting a cheaper modification than the copper 

 and iron gas-grate, we should before very long observe a marked 

 change for the better in our London atmosphere; and the dark- 

 ness, dirt, and destruction of property w ith which we Londoners 

 are annually afflicted, would be things of the past. 



December 13 R. Douglas Hale 



Geological Climates 



I have just read Mr. A. R. Wallace's letter in Nature, vol. 

 xxiii. p. 124, but as I have not yet seen his book, " Island Life," 

 although my bookseller had promised it, I shall defer my reply 

 in Nature until I shall have made myself master of his ideas. 



For the present I shall only say ; — i. That Mr. Wallace's pro- 

 posal would benefit the Tolar regions but not Bournemouth. 

 2. Mr. Wallace omits all mention of the return cold currents 

 which the admission of two new Gulf Streams into the Arctic 

 regions would produce. These currents would seriously lower 

 the temperature of China and Japan ; and also of the Ural 

 Mountains and east of Europe. 



Samuel Haughton 



Trinity College, Dublin, December 10 



Some weeks since the Rev. Prof. Haughton took exception 

 to a brief letter of mine, in which I suggested that as a bamboo 

 flourishes in Cooper's Hill College garden, in a northern aspect 

 winter after winter, it could be used effectually in an argument 

 relating to geological climates. The bamboo being found in 

 torrid India now, fhat at Cooper's Hill, if found in a future 

 period, iiould, according to some geologists, indicate that the 

 valley of the Thames was tropical formerly. My letter was 



