On Electrotyping Operations of the U. 8. Coast Survey. 311 
tially recommended by all the writers on electro-metallurgy, the 
arrangement being such as to produce good metal. 
now evolved in thirty minutes was found only one-twentieth of 
the former amount; hence the introduction of the resistance, ft, 
had diminished Q twenty times, and Ray =Q=5)5 R Whence 
risequal to 19 R. ‘To exhibit the effect of battery enlargement, 
we now have Q=i7749 If m=1, then Q=05; if m=2, 
Q=0512; if m=3, Q=-0518; if m=4, Q=-0524, &e., &e. 
This shows a gain of only a fortieth from doubling the size of 
the battery, &c.—an advantage too small to repay for the en- 
lagement. ‘These calculations are in accordance with experi- 
mental results from small batteries, but in large ones the neces- 
sity of further separating the plates, in increasing their size, 
makes the resistance increase, instead of diminish, and there is 
consequently a loss from enlargement. It is not, therefore, by 
merely increasing the battery surface that the time for electro- 
typing can be shortened. 
t. Smee, the distinguished writer on electro-metallurgy, by 
covering the negative plate of the battery with pulverulent pla- 
num, produced a very energetic form of the instrument. en 
plate is freshly platinized, it acts violently, and throws off 
the hydrogen in torrents. But this increased energy of the plate 
S$ gradually lost, from the electric current depositing upon it 
npurities from the zine. ial 
S this deposit has a strong attraction for the hydrogen, it is 
‘ttm which would restore the original platinum to its energy. 
This I attained, at length, by immersing the plate in a solution 
of per-chlorid of iron, which almost immediately restores the 
the decomposing cell, the time for making a casting was re- 
This is * peep E in the formula, and this will sometimes in- 
a We unite the effective force of many batteries by joining their 
dissimilar ends in consecutive order. As the current in such an 
