ON UNDERGllOUND TEMPERATUBE. 255 



having been allowed to the thermometer. The reading in these repeated 

 experiments at 644 feet, with ample time, was a normal one between tho 

 readings above and below." 



It having been ascertained that the slipping-down of the mercurial index, 

 which has often occurred in the Phillips thermometers supplied to the Com- 

 mittee by Casella, was owing to their bore being less fine than in the origintd 

 instrument as designed and constructed by Professor Phillips, two thermo- 

 meters of finer bore were ordered from Casella ; and they have been found to 

 exhibit as much stiffness in the index as is desirable — so much so that diffi- 

 culty is sometimes experienced in shaking the index down to its place when 

 the instrument is to be set. The thermometers thus constructed have the 

 advantage of great qi\ickness of action, as compared with the large-bore 

 Negrettis which are in \ise by the Committee ; but the excessive fineness of 

 the bore sometimes occasions difficulty in reading. The instrument, in fact, 

 could scarcely be put into the hands of any one but a skilled observer. 



Two thermometers were supplied to Mr. "Willett, the Honorary Secretary 

 for the Sub-Wealdeu bore which was commenced last year at Netherfield. 

 One of them was a Negretti, the other one of the new fine-bore Phillips 

 thermometers above described : the former alone was used. The first 

 observation was taken in April of the present year by Mr. Bosworth, the 

 engineer of the boring, and showed a temperature of 68 1° Fahr. at the depth 

 of 168 feet, the temperature of surface-springs as tested by the same instru- 

 ment being 51° F. The Eeport states that the thermometer " appears to do 

 its work well, and to give reliable results." In a second observation, taken 

 in Mr. Bosworth's absence, the instrument was broken in hauling up. 

 Another thermometer of the same kind was then procured from the makers ; 

 and an observation taken with it on the 2nd of August showed a temperature 

 of 62° F. at the depth of 263 feet. No observations were taken except at 

 the bottom, on either occasion ; and the above numbers show that the heat 

 generated by the boring-tool was sufficient to produce disturbances of tem- 

 perature amounting to several degrees. 



Thermometers have also been supplied for observations in two deep wells 

 in Essex — namely, one at Witham, 660 feet deep, and another at Harwich, 

 originally about 900 feet deep. The commencement of the observations, 

 however, has been hitherto delayed. 



There is a well at Comb's tannery, near Stowmarket, which was sunk 

 some years ago to the depth of 895 feet, the first 57 feet being clay and sand, 

 and the remainder chalk and marl, except about 20 feet of gault and green- 

 sand at the bottom. The proprietor, Lankester "Webb, Esq., on being applied 

 to, near the close of last year, at once, in the most obliging manner, undertook 

 to make observations of temperature in it ; and a l^egretti thermometer was 

 supplied for the purpose. 



On proceeding to take the observations, it was found that only the first 

 283 feet were available, the remaining portion of more than 600 feet being 

 choked with chalky mud. Three sets of observations were taken, with the 

 following results : — 



Temperatures in degrees Falir. 



1st set. 2ucl set. 3rd set. 



3 feet from surface of water 54 



100 „ „ groiuid 52^ 52* 53 



150 „ „ „ 53 



200 „ „ „ 54 54 53 



283 .524 54 54 



