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Mr. Lane on Electric Conductio 
such operations, I have only made a single experiment with par- 
tially purified mercury in glass tubes. ‘The arra 
in fig. 5. abed the gauge wire used as be 
ANEOUTE CFG LIE EUS 
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tubes of mercury, terminated by woe den cups, and the whole 
connected together as shown in the figure. ‘The cups were 
pierced with brass pinsa’, 6’, f Fig. 5. 
ce’, d’, reaching almost to the 
extremities of the tubes,* 
and varnished within the 
cups, except at the points, where the varnish was ground off. On 
passing a current between P and N, it would be divided between 
the gauge wire and the tubes of mercury, and the tension at the 
extremities of the latter could be ascertained by severally con- 
necting the pins a’, b’, c’, d’, through the galvanometer, with the 
corresponding points of equal tension a, 6, ¢, d, on the former. 
With a single pair of Smee’s battery, in imperfect order and 
weakly charged, the result was, 
ab=45°619 in. ed = 15°825 in. 
Tube a’b/=20-050 “ Tube c/d’=15-097 “ 
Weight of mercury in tube a’b/= 14-095 grammes. 
“cc 66 ‘c c! /—=—23-004 66 
Let ab=L, a’b’=1, weight of a’b’=w, and section of a/b’ =5, 
: . w! 
cd =L/, cd’ =I’, weight of c'd’=w’, and section of e’d’= T: 
Then if we adopt the first proposition, and assume the second 
which is to be proved, ab, which of course varies directly as the 
length of a/b’, must vary inversely as its section, or L varies as 
23 
aa ant or Lais as 72; i.e. Lab 3 L’w': 10? 3 1, and l?Lw=2L'w’. 
i ee, 
Now in the above experiment we shall find that 
V2 Lao : 12/0’: :705 ; 704. 
Se enigma 
* A minute space was left between the end of the tube and point of the pin, on 
account of the obstruction of the current by the latter. For a very accurate ex- 
periment, it would be better to pass the pin through the side of the tube, at a little 
distance from the end. It may be worth while to state, that at first very fine sew- 
ing needles were used in place of the pins, and with these none but a strong cur- 
rent would pass to the galvanometer. No attempt was made to amalgamate the 
steel points, but the brass pins were substituted at the suggestion of a friend, to 
whose kindness I am much indebted. 
