54 
THE VOYAGE OF H.M.S. CHALLENGER. 
1 m ■ ■ ^nrv apparatus in my laboratory to attempt to do this, and besides had 
been informed that the problem was likely to be taken in hand by Professor Tait. 
A notice in the Royal Society of Edinburgh’s Proceedings for 1882-83, p. 45, 
indi. at - that he has done so, and 1 hope that his results may enable him to give 
it formula for the reduction of Mr. Buchanan’s specific gravities of deep sea-waters 
t.' their actual pressures in situ* 1 confined myself to determining the influence on the 
specific gravity of concentration and temperature. For this purpose I carried out the 
following series of experiments : — 
L Si • A number of the more saline of ( hallenger waters were mixed together, so 
i t" pmduee several litres of a sen-water containing about 20'5 grins, of chlorine per kilo, 
i \ 20*5 h The specific grax ity of this water was determined at 12 different tempera- 
tun • g ng from —3 l to +29 *45 C., by means of a glass plunger, which, by a 
vious series of experiments (ranging firom 6 e, 6 to 30°*6) had been ascertained to 
displace the volume of 1907144 grins. + 5'8 xt mgrms. of water of 4°, at t° C. In the 
exp- riments the plunger was suspended from the bottom of one of the pans of an Oertling 
1 inch balance, bj means of a line platinum wire, while the water or sea-water operated 
upon was contained in a large cylinder standing within a large water-bath (of 30 — 40 litres 
i -i pucity), which served to maintain a constant temperature. At temperatures differing 
fr<»m tint <»f the room, the temperature of the bath was kept uniform by constant agitation 
with a perforated horizontal plate fixed to a vertical rod, while the plunger itself served 
for mixing together tin- water to be tested. A small bulb thermometer, divided into 
l nth'"t a di-gr- e, wjus constantly kept immersed in the latter. As soon as a constant 
j w ' -i al.li'hed, this temperature was maintained for a time, and the apparent 
v. • _iii tli- imim r ■ d plunger determined two or three times in succession so as to make 
-ur.- in this manner of perfect equilibrium of temperature. Previous to the last weighing, 
• \ In d* i iii tin piling' i w; lifted out of the hath for an instant, to make sure of the 
"11 . or to iviin.v any that might show themselves, which, however, happened 
i ■ tinn - at th liigln-r t- mperatun The ^ of the water had been previously 
;i diipli<-ati amdy'i- (by our ivfincmeiit oil Volhard’s method), and was again 
"i tin p.-.-ifie gravity experiments, when it turned out that, by the unavoid- 
t "ti at tin login i t- nip ratun -s, it ^ had increased by about 0*05 unit. The 
•i tl < • 1 • n 1 1 1 i« m wa- ^ 20 523. The specific gravities! 4 S 0 or rather 
v * • • -r tin minimum vahn-, w« -re laid down us ordinates, the corresponding 
- ' i a in a sy-tem of n-ctangular coordinates, and united by the nearest 
- •• • I-. it* - of which st-rved for the calculation of an interpolation-formula — 
t.i N<>. I 14) < 1 f tin I’r . Hoy. Soc. Edin., Professor Tuit has given for sea-water 
aft 1W C. ilk* following value < .<• com pit I per square inch (about 150 atmospheres) 
' r H< r. i r* | - ■ nts ili. nnmL rof ton's weight per square inch to which the water was at first 
• it rvprnwnU (very nearly) the <iepth in mile* under the surface. 
♦ ,H, mewn*— gravity at (° referred to water of 4° a* » 1000. 
