16 



THE VOYAGE OF H.M.S. CHALLENGER. 



correction of this kind need be made in experiments on fresh water between 0° and 

 8° C, but for higher temperatures it rapidly came into play. In the case of the 

 stronger salt-solutions it was always recpuired. 



As an example of the general dimensions of the piezometers, I print here the 

 details of a rough preliminary measurement of one only ; and employ these merely 

 to exhibit the nature of the calculation for the compressibility of the contents. 



Measurements for (:). 



21/12/86. At temperature 3° C. (:) filled with Portobello sea-water gave for 

 413 of gauge (about 150 atm.) 131-2 of displacement for index. 



834 „ „ 300 „ 256 



1254 „ „ 450 „ 373-6 



Before pressure, mercury 20 mm. from enamel. 



This experiment is selected because its data were taken for the approximate lengths 

 of the columns of mercury used to calibrate the stem of (:). 



22/6/87. Length of col. of mercury in stem. 



End 18 mm. from enamel 130'S mm. 



Weight, mercury and dish. 

 12-567 grin. 

 Dish 9-387 „ 



Hg. 3-180 



15-712 grin. 

 9-387 „ 



Hg. 6-325 



18-407 grm. 

 Dish 9-387 „ 



Hg. 9-020 „ 



Weight of dish with Hg. filling bulb and stem to 599 mm. from enamel, 517-63 „ 



Weight of dish, 37-69 „ 



Hg. in piezometer, less 599 of stem, 479"94 „ 



Hg. in 599 of stem, 14-56 „ 



"Whole content to enamel, 

 „ 20 from enamel, 



494-50 

 494-0 



