318 On Electrotyping Operations of the U. 8. Coast Survey. 
ance. On first immersing the plate, the solution should, there- 
fore be perfectly clean. Formerly, after each use of the vertical 
vat, it was emptied and washed out. When the solution had de- 
posited its sediment it was drawn off and strained through very 
fine cotton. ‘This whole operation was extremely disagreeable, 
and consumed a whole day of one man. 
a simple expedient I have saved the necessity of cleaning 
the vat oftener than once a month. ‘T'o guard the new plate 
from specks and impurities, a bag of fine cotton is drawn over a 
slight. wooden frame, which keeps it distended. An hour or 
more before the solution is wanted, the bag, with its included 
frame, is placed on top of the solution and loaded with the cop- 
per bars used to support the plate frames. ‘The weight causes 
the bag to sink gradually, filtering the contained solution as it 
goes down; the impurities cannot wholly choke the meshes 
of the cloth, asa fresh portion is constantly brought into action 
during the sinking. I thus filter the solution without taking it 
from the vat or disturbing the sediment, saving much labor, time, 
and annoyance. 
The plate remains in the vertical vat over night, and prepara- 
tions are made in the morning to transfer it to the horizontal vat. 
The furnace is first brought into action. A new plate of blan 
copper, an inch larger than the matrix, is flattened on the iron 
table, and bolted to the edges of wooden bars by platinum bolts, 
. for the purpose of preventing the plate from sagging downwa 
when supported horizontally. The plate so arranged is called 
the strapped plate. The coated matrix is then taken from the 
Vertical vat, disengaged from its frame, and arranged in the hori- 
zontal frame. A wooden wall, an inch high, then surrounds the 
plate, and on this wall the strapped plate is laid, when the whole 
combination is placed in the horizontal vat and the connection 
with the battery established. The positive plate is then taken 
from the vertical vat and its loss of weight noted and recorded. 
From the known superficial area of the matrix, the quantity of 
copper required for a casting one-eighth of an inch thick is com- 
puted and recorded. The blank copper consumed in both vats 
must equal this amount before the required thickness is reached, 
allowance being made for impurities of rolled copper and rough 
ey will begin to drop on the electrotype; this plate went 
therefore, be removed from the vat and a new one imm 4 
supplied. The dirty plate is then washed in the large water ¢ 
and when cleaned j ; 
the amount of loss the action of the batteries is tested, and It 
found, if Smee’s laws are being observed. Vigilance must now 
be exercised in watchin ies and rate of work, and the 
power must be varied to suit circumstances. 
aned its loss of weight is found and recorded. Y 
