44 report — 1879. 



The observations appear to have been taken in very favourable circum- 

 stances, and with much care and judgment. Being the only observations 

 yet furnished to the Committee from the West of England, they form a 

 very valuable contribution to our knowledge. 



Mr. Symons has continued his observations at the depth of 1000 feet 

 in the Kentish Town Well (see Report for 1876, p. 209). During 1877 

 little was done except to continue the record of the temperature of the 

 well-room, have the roof repaired, and make experiments with respect to 

 the elongation of wires of various kinds. In accordance with a suggestion 

 of Sir William Thomson, a new copper wire, No. 22, was purchased, 

 and the Phillips's maximum thermometer, No. 14,608, of which each 

 degree Fahr. is 0"4 inch in length, was lowered to 1000 feet on January 10, 

 1878. The first noticeable feature, and a very unsatisfactory one, was, that 

 on March 5, 1878, a little mud was found in the protecting case. It will 

 be remembered that the tube was originally 1302 feet deep, but that on 

 the first attempt to lower the thermometer to 1100 feet in May, 1868, the 

 cord was found to become slack at depths varying from 1070 to 1085 

 feet. It seems probable that the mud has now risen to 1000 feet. Its 

 extreme softness has been illustrated more than once by the fall of 

 thermometers into it, sometimes from a great height. They have never 

 been broken, nor even had their indices displaced. The new wire stretched 

 more than the old one, but after the first two months the elongation was 

 remarkably uniform. The thermometer having been many years in use, 

 it was thought desirable to reverify it, and on September 20, 1878, it was 

 sent to Kew Observatory for this purpose. Another thermometer was 

 temporarily substituted for it, which was only divided to whole degrees 

 and was read by estimation to tenths. With this thermometer the 

 following observations were taken : — 



Date of lowering Depth indicated Date of raising Depth indicated Temperature 

 Feet Feet Fahr. 



1878, Oct. 10 1000 Nov. 2 1009 67-8 



Nov. 2 1000 Dec. 2 1008 67"8 



Dec. 2 1000 1879, Jan. 2 wire broke 



The wire broke on January 2, 1879, and up to the present time no 

 serious attempt has been made to recover the thermometer, but this has 

 arisen rather from want of leisure than from any difficulty in the 

 operation. 



The results given in the following table (which goes back to the 

 beginning of the observations), have all been obtained with one and the 

 same thermometer. 



The index error of the thermometer has been determined several times, 

 .as follows : — 



1872, August, by Mr. Symons, error under + -0 1 



1873, November, by Professor E. J. Mills error + -34 

 1876, February, by Mr. Oasella „ + -5 

 1878, December, by Kew Observers „ + -5 



The gradual rise of zero here indicated is in accordance with usual 

 experience ; and the index errors at intermediate dates have been derived 

 from these by graphical interpolation, that is by drawing a curve in which 

 horizontal distance represents time and vertical distance amount of index 

 error, the curve being drawn so as to pass through the four points 

 determined by the above observations, and being made as smooth as 

 possible. The stretching of the wire is determined by the readings of the 



