70 
THE VOYAGE OF H.M.S. CHALLENGER 
th. n S will have a different value 1000 + //. To find y, operate as shown in Column IV. 
of tlx laid . The formulae terminating with ±0*00 . . . are calculated for S = 1025, 
and the uncertainty is given on the assumption that the formula be applied to S = 1020 
to S= 1030 as extreme cases. 
'1'h. Table VII. which now follows is intended for the reduction of the specific 
,S oi a sea-water from 15°‘5G to any temperature t° between 0° and 31°, and 
kl The table is an extension of Table \ hence there is no need of its being 
explained in general terms ; but for the convenience of any person who may wish to use 
it. I will give two examples. The specific gravity 4 S of a sea-water is 1027*34 at 
15 *56 ; how much is it at 18 *3 ? Answer: At 15°*56 the water is heavier than standard 
r by 1*84, hence at 18°*3 it is heavier than the latter by 1*34 x <£(18*3) = by ; 
table to 1*34 x0*9937 = 1*332; but standard water, by table, at 18 0, 3 has the specific 
gravity 1025*34, hence the result is 1025*34 + 1*33 = 1026*67. Second Example. — Given 
the specific gravity at 18 *3 as 1026*67 ; find the specific gravity at 15°*56. Answer: At 
18 *3 the specific gravity of the given water is 1026*67 — 1025*34 = 1 *33 heavier than 
standard ; hence the corresponding difference at 15°*56 is 1;33 .^ 3 . 3 ^ = by table to 
1*33 x 1*0063=1*34 ; hence result sought =1026*0 + 1*34 = 1027.34. This is the result 
a< • onling to Dittmar ; if Thorpe and Rucker's function be preferred, add (in the sense of 
nl _r* bra) the correction given in Column V. to the specific gravity of standard ivater at t° 
winch enters the calculation. This correction of course is nil for £=15°*56. 
Table VII. 
To find Specific Gravity 4 S, at 1 from given Specific Gravity at 15°*56. 
.. i 
I. 
IL 
III. 
IV. 
V. 
Specific Gravity of 
] 
Correction for 
• • 
Standard Water, 
*(')■ 
to find Tli. and R.’s 
Dittmar. 
W) 
result. 
0 
1028 18 
1-0514 
•9511 
+ 069 
0 1 
•18 
1 0509 
•9515 
•067 
*2 
•17 
1 0505 
•9519 
•065 
•3 
17 
1 0500 
•9524 
063 
•4 
•16 
1-0496 
•9528 
•061 
•5 
•16 
1-0491 
•9532 
■059 
•6 
1ft 
10486 
•9536 
•056 
•7 
1ft 
1 0482 
•9540 
•054 
•ft 
14 
1 ’0477 
•9545 
•052 
O 
•14 
1 0473 
•9549 
•050 
