ON UNDERGROUND TEMPERATURE. 159 



The tunnel has now been carried to a distance of 2500 metres at the Swiss 

 and 2200 metres at the Italian end ; and the temperature of the rock, as 

 deduced from air-observations, is — 



At 2400 metres from Swiss portal 21°-7 C. 



„ 2180 „ „ ItaHan „ 21°-3 C. 



The distances from the surface (measured in the nearest direction) are 306 

 metres in the former case (the plain of Andermatt being overhead), and 

 1090 metres in the latter. The mean temperature at Gosclienen (the village 

 at the Swiss end) is 6°-82 C. 



Observations were taken (Aug. 17th, 1874) by Mr. John Donaldson, C.E., 

 ill a pump-well 413 feet deep, at Mr. Sich's brewery, Chiswick, near London, 

 The pumps were kept idle all day to facilitate observation. The thermoincter 

 used was a protected Phillips's maximum. During the first series of obser- 

 vations, pumping was going on from a well in a neighboiiring brewery, an 

 operation which lowers the level of Mr. Sich's weU by about 3 inches. This 

 pumping was discontinued before the completion of the second series. The 

 surface of the water is 60 feet below the surface of the ground. The diameter 

 of the well is 5 feet to the depth of 200 feet, and is less than one foot (and 

 gradually diminishing) for the remainder of the depth. The following are 

 the observations : — 



Depth from Temperature in degrees Fahr. 



surface of , » n 



ground. First Series. Second Series, 



ft. in. o o 



65 o 55'S 56-2 



i°S 6 546 54-5 



iSS 9 545 54'S 



2°5 9 54'9 55"o 



256 25 5S"° 54"9 



306 7 55'S S5"4 



358 I 56'6 56-6 



395 5 57-5 58-0 



The difference between the two obseiwed temperatures at 65 feet is attributed 

 to the disturbance of the water by passing the thermometer and suspending 

 wire through it. The difference of half a degree between the two observationg 

 at the bottom is attributed to the discontinuance of pumping in the next 

 brewery, as mentioned above. These temperatures (57°-5 and 58"-0 at the 

 depth of 395 feet) may be compared with the temperatures observed by 

 Mr. Symons in the Kentish-Town well at the depth of 400 feet, as given 

 in our Reports for 1869 and 1871, namely 58°-l and 57°*9. The agreement 

 is satisfactory, as indicating, on the one hand, that even where there is 

 strong convectivc action (as in this pump-weU) the temperature near the 

 bottom is but slightly affected; and, on the other, that where there are 

 no strong springs the temperature at intermediate depths (the Kentish- 

 Town well being 1100 feet deep) is likewise nearly free from couvective 

 disturbance. 



A boring in search of coal is being made at Swinderby, about eight miles 

 to the west of Lincoln, in which observations have been made by Mr. J. T. 

 Boot, the engineer of the works. The depth attained on July 19, 1875, was 

 1535 feet, the strata penetrated being :• — (1) Lower Lias, 140 feet ; (2) Kew 

 Eed Marl (Keuper), 569 feet ; (3) New Red Sandstone (Keuper and Bunter), 

 790 feet. The boring is now in red marl of the Permian formation. A great 



