ON UNDKlteilOUND TEMPERATURK. 



209 



india-rubber bags, filled with water, and pressed, not by screwing, but b}- 

 the weight of the rods, were employed with much satisfaction. 



All the methods of plugging employed by Herr Dunker involved the us*^; 

 of the iron rods belonging to the boring-ajiparatus, and therefore would be 

 inapplicable (except at great expense) after the operation of boring is finished 

 and the apparatus removed. 



It seems desirable to contrive, if possible, some plug that can be let down 

 and raised by a wire. In the first report of your Committee, it was suggested 

 that two bags of sand, one above and the other below the thermometer, 

 should be used for this purpose. Bags of sand, however, would be liable to 

 rub ofl:' pieces from the sides of the bore, and thus to become jammed in 

 drawing up. Mr. Lebour has devised a plug which will be of small diameter 

 during the processes of lowering and raising, but can be rendered large and 

 made to fit the bore, when at the proper depth, by letting down upon it a 

 sliding weight suspended by a second wire. Sir W. Thomson suggests that 

 a series of india-rubber disks, at a considerable distance apart, will pro- 

 bably be found efi"ectual. 



Mr. Boot has continued his observations in the bore which he is making 

 at Swinderby, near Scarle (Lincoln). It has now been carried to the depth 

 of 2000 feet, and is in earthy limestone or calcareous shale, of Carboniferous 

 age. Its diameter in the lower part is only 3^ inches. In April last the 

 temperature 78° F. was observed at 1950 feet ; and more recently 79° F. 

 was observed at 2000 feet — the water, in each case, having been undisturbed 

 for a month. Supposing these results not to be vitiated by convection, and 

 assuming the mean temperature at the surface to be 50°, we have an increase 

 of 29° in 2000 feet, which is at the rate of 1° in 69 feet. 



Mr. Symons has taken a series of observations at the depth of 1000 feet in 

 the Kentish-Town well, with the view of determining whether the tempe- 

 rature changes. The instrument employed is a very large and delicate 

 Phillips's maximum thermometer. The following is a list of the obser- 

 vations : — - 



i Date of lowering. 



1874, — 

 May 



July 

 .Tulj- 

 Sept, 

 Sept. 29 

 Oct. 30 

 Dec. .3 

 ISTi'). Jan. 

 Feb. 

 Mar. 

 Maj- 

 June 

 July 

 Aug. 

 .Sept. 

 Oct. 

 Oct. 

 Nov. 



8 

 2 



28 

 8 



10 



Depth 

 indicated. 



10 

 1 



feet. 

 1000 

 1000 

 1000 

 1000 

 1000 

 1000 

 1000 

 1000 

 1000 

 1000 

 1000 

 KXtO 

 1000 

 1000 

 1000 

 1000 

 1000 

 1000 

 1000 



Thermo- 

 meter 

 set at 



64-50 

 63-80 

 63-20 

 65-10 

 65-80 

 65-81 

 63-40 

 63-80 

 63-75 

 63-90 

 03-90 

 03-95 

 63-00 

 03-87 

 63-87 

 64-00 

 63-9() 

 63-80 

 63-70 



Date of 



1874, May 8 

 July 2 

 July 28 

 Sept. 8 

 Sept. 29 

 Oct. 30 

 Dec. 3 



1875, Jan. 7 

 Feb. 1 

 M.U-. 3 

 May 3 



1 

 7 

 3 



Depth 

 indicated. 



June 

 July 

 Aug, 

 Sept. 10 

 Oct. 2 

 Oct. 19 i 

 Nor. 1 . 

 Dec. 1 I 



feet. 

 1007 

 1009 

 1005 

 1004 

 1004 

 1000 

 1006 

 1009 



loor, 



1005 

 1006 

 1005 

 1005 

 1(KJ4 

 1001 

 1003 

 1004 

 1005 



Temperature 

 Fahr. 



66-82 

 (reading lost.) 

 67-40 

 67-51 

 67-43 

 67-68 

 67-52 

 07-63 

 67-56 

 67-58 

 (;7-62 

 07-49 

 G7-53 

 67-58 

 67-58 

 67-58 

 67-62 

 67-62 



Wire broke. 



1876. 



