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On Electrotyping Operations of the U. S. Coast Survey. 307 
The method nsed in the British ordnance survey is perhaps 
the best of all these. ‘This is conducted as follows: The plate 
is fitst well oiled, and the oil well wiped away with soft bread. 
The plate is then heated to above the temperature of melting 
wax, and a cake of white wax pressed against the edge. The 
_sithaving removed the air from the plate, the wax will flash 
over it in an extremely thin sheet or film. All excess of wax is 
en to be wi away with a fine linen cloth, free from lint. 
The plate must be left to cool before introducing it into the vat. 
To smear the face of the finely engraved plate is in opposition 
‘9 the fundamental idea of the electrotype, which is that of 
atomic casting. In the process of Mr. Smee, air bubbles will be 
Mained in the fine lines of the graving, thus mutilating the 
“Py; Moreover, the face of the new plate is waved from the 
ailation of the stratum of air when receiving the first portion of 
copper. . 
fa the Waxing process it is almost impossible to free every 
line from excess of wax. Even days of tedious application do 
tot insure perfection. In addition to the éoarseness of these va- 
tous methods, they are extremely uncertain as to whether they 
effeet the purpose for which they are applied. 
It was always observed that if the deposited metal was not de- 
in mechanical properties, it stuck very hard to the original, 
aid the plates had to be subjected to violent jarring, heating and 
beating, to separate them. But if the deposited metal was of 
ella quality, then most fikely the deposit was inseparably 
United to it. From these circumstances attending the adhesion 
lb Considering the sticking of the plates, after homogeneous 
faction or cohesion, heterogeneous attraction or adhesion de- 
