136 On the Construction of De Luc’s Columns. 
Arr. XVII.—On the construction of De Lwuc’s Columns, as modi- 
jied by Zamboni: and on the modification of the single leaf Elec- 
_ trometer contrived by the author, by. which the possible efficiency of 
a large electric series, may be ascertained, by testing a small por- — 
tion of the members of which it is to be constituted. Also on the 
employment of the same instrument, as an Electrical Discrimina- 
tor: by Rosert Hane, M. D., Professor of Chemistry in the 
University of Pennsylvania. 
Communicated by the Author. 
Asovrt fifteen years ago the construction of De Luc’s electric col- 
umns‘as modified by Zamboni, was undertaken by Isaiah Lukens, one 
‘of our most skillful and ingenious: mechanicians. 
The materials employed were paper covered with leaf tin, “oa 
neously called silver paper,) peroxide of pati arise and = 
sulphate of zinc. 
The pictonider’ was finely pulverized, and ileed with a concentra- 
ted solution of the sulphate. The mixture thus formed was, by 
means of a brush, applied like a pigment to the surfaces of the pa- 
per not coated by the tin. The sheets were afterwards spread out 
on the floor of an apartment and left during the night to dry. By 
these means, unnecessary exposure to light was avoided, which Mr. 
Lukens, conceives to be injurious, especially as received directly 
from the sun. Next day the sheets were cut into disks of about five 
eighths inch diameter, by means of a hollow punch. The disks 
were then piled with the heterogenous surfaces alternating, as in 
other voltaic series, and were introduced into, and compressed with- 
in, glass tubes, accoutered as usual with pedestals, caps and bells. 
Notwithstanding his skill and experience, Mr. Lukens, latterly com- 
plained of occasional want of success, arising, as he supposed, from 
the defective quality of the manganese. In various instances, his 
columns, after being completed with the utmost care, proved inert. 
The manipulation, likewise, according to his plan of operating, 
appeared to me, to be troublesome and precarious. He was accus- 
tomed to place a row of the disks, as large as could be conveniently 
handled, in a trough of sheet metal; and then transfer the pile thus 
formed to the glass tubes. This operation, to be successful, requi- 
red dexterity. 
