HYJ>r^OGllAPHICAL SURVEY. 



195 



TABLE. 



This degree of impregnation is not surprising, 

 when we consider that the pressure of water, at the 

 depth to which these specimens of wood were sent, 

 is equal, at least, to 2031 /&. or l^cwt, \5lb. on 

 every square inch of surface *. 



* According to the estimation of Sir George Shuckbm-gh 

 Evelyn, (Phil. Trans, vol. Ixxxviii.), corrected by Mr Fletcher, 

 (Phil. Joiu-n. vol iv.), a cubic inch of distilled water, tempera- 

 ture 60°, weighs 252.5060 grains, being the usual unit of spe- 

 cific gravities, or 1.000. The mean specific gravity of the 

 Greenland Sea, included between the parallels of 76° and 

 79° N, is, at temperature 60°, 1.0264, and at 30°, (the mean tem- 

 perature of the water at the surface), 1.028; hence. As 1.000., 

 the specific gravity of pure water, is to 252.506 grains, the 

 weight of a cubical inch of pure Avater, so is 1.028, the specific 

 gravity of the water of the Greenland Sea, to 259-5761, the 



N 2 



