Chap. 4.] at different Depths. 477 



depths, in the following terms : " Tht apparatus for 

 trying the heat of the fea water at different depths 

 confided of a fquare wooden tube of about 18 inches 

 long and three inches fquare externally. ' It was fitted 

 with a valve at the bottom, and another at the top, 

 and had a contrivance for fufprnding the thermometer 

 exactly in the middle of it. When it was ufed it was 

 fattened to the deep fea line, juft above the lead, fo that 

 all the way as it defcended the water had a free paiTage 

 through it, by means of the valves which were then 

 both open; but the inftant it began to be drawn up, 

 both the valves clofed by the prefihre of the water, 

 and of tourfe the thermometer was brought up in a 

 body of water of the fame temperature with that it 

 was let down to *." With this inftrument, which is 

 much the fame with one formerly defcribed by Mr. 

 Boyle, in his obfervations about the faknefs of the fea, 

 water was fetched up from different depths, and its 

 temperature accurately noticed, in different feafons and 

 latitudes. 



f Auguft 27, 1772, fouth latitude 24. 40'. Hie 

 heat of the air was 72!, of the water at the furface 

 70, of water from the depth of 80 fathoms 68 f. 



c December 27, 1772, fouth latitude 58. 21'. 

 The heat of the air was 31 , of the water at the 

 furface 32, of water from the depth of 160 fathoms 



Mft- 



( In the voyage to the high northern latitudes be- 

 fore mentioned, they made ufe of a bottle to bring up 

 water from the bottom, which is thus defcribed. 



* See Agronomical Obfervations made in a Voyage towards 

 the South Pole, &c. in 1772, 1773, &c. by W. Wales. Intro- 

 duftion, p. 53. 



f Wales's Obfer. p. 206. 



J Ibid. p. 208. 



Th 



