1902-3.] Mr Manley on Electrical Conductivity of Sea- Water. 355 
with the index line m ; it was then secured in this position with 
the clamp (Position B). Data for the new resistance were then 
collected by proceeding in the manner given above. 
From the data obtained with the movable electrode in the 
Positions A and B we can calculate (1) the resistance B of the 
cell leads plus that of a short column of sea-water of unknown 
though constant magnitude ; and (2) the total resistance B', due 
to the two factors enumerated under (1), together with that of a 
column of sea-water of known length and cross-sectional area. 
Hence the resistance X 2 of the added column of sea- water will be 
equal to the difference between B and B', or 
X x = B' - B. 
The resistance B was calculated from the formula 
2010 -{r-r} B 
2010 + {r-/} “ S’ 
in which 2010 is the practical length of the bridge wire in milli- 
metres ; r and r the two mean readings obtained, the former with 
the standard coils S in the left-hand gap of the bridge, and the 
latter after reversing the positions of S and the conductivity cell. 
With the aid of the proper temperature coefficient (vide infra) r 
X 1 is readily reduced for the standard temperature of 24° C. 
Xow since the dimensions of the added column of the sea- water 
are known ( vide supra), the specific resistance p 24 of the water 
at the standard temperature may be calculated ; the reciprocal of 
1 
this, — , will be the specific conductivity sought. 
P24 
Two other sets of observations made at higher temperatures 
were similarly treated and reduced, and the means of the three 
independent results taken as the true values for p 24 and — . 
P24 
All the samples of water were examined in precisely the same 
way. 
Determination of Temperature Coefficients. 
The temperature coefficient for each of the five samples of water 
was deduced from the three resistances X x , X 2 , and X 3 , which the 
added column of sea-water was found to possess at the respective 
temperatures of t v t 2 , and t 3 ; the values selected for those tempera- 
tures being approximately 10° for t v 15° for t 2 , and 20° for t. d . 
