CHAP. VII. J 



DEEP-SEA TEMPERATURES. 



21)5 



depths in the ocean, to determine the amount and 

 sources of error, to ascertain which was the most 

 satisfactory instrument, and if possible to construct 

 a scale by which the observations hitherto taken 

 with ordinary instruments might be roughly cor 

 rected, so as to be made available. As there was 

 some difficulty in getting the use of a suitable press, 

 Mr. Casella undertook to have a testing apparatus 

 constructed at his own place in Hatton Garden, 

 capable of producing a pressure of three tons on 

 the square inch. 



The results were very interesting. 1 The first expe 

 riment went to test the value of the various instru 

 ments. A Miller-Casella thermometer was placed in 

 the cylinder with No. 57, a good thermometer by 

 Casella, of the ordinary Hydrographic Office pattern, 

 and they were subjected together to a pressure of 

 4,032 Ibs., equal to 1,480 fathoms, with the following 

 result : 



That is to say, the temperature remaining the same, 

 the pressure forced up No. 57 to 12- 75 C., and left its 

 index there. 



i On Deep Sea Thermometers, by Captain J. E. Davis, RK Nature, 

 vol. iii. p. 124. Abridged from a Paper read before the Meteorolo 

 gical Society, April 19th, 1871. 



