I2 
paper is used as the medium, an image of the coin is 
formed upon the paper. This image becomes visible 
on treating the paper with nitrate of silver and hydro- 
quinone. The undeveloped image will remain several 
weeks unimpaired. A suggested explanation of this 
effect is that metal from the zinc plate is carried by 
the current into the paper. It is then assumed to be 
capable of producing chemical changes, which result in 
the production of images when the paper is treated 
with suitable chemicals. Other suggested explana- 
tions are, the production of peroxide of hydrogen by 
the current, and the presence of an electric charge. 
But none of these explanations account for all the 
observed phenomena. When the paper is first treated 
with nitrate of silver and the current is afterwards 
passed, a deposit of the metal is obtained on the 
surface of the paper where there is contact. In this 
way by using printers’ type, a perfect copy of the 
letters is formed. Printing may thus be performed by 
electricity without ink, 36,000 copies per hour being 
possible with suitable machinery. By treating the 
paper with different chemicals prints of different 
colours can be obtained. 
Friday, March 6th. Sir Samuel Wilks, Bart., 
F.R.S., President, in the Chair. 
Mr. A. W. Stokes, F.C.S., F.I.C., gave a 
lecture on ** A Cup of Tea,’’ which was illustrated 
with lantern slides. He pointed out that all nations, 
wild or civilized, had found it necessary to concoct 
drinks more stimulating than water. These may be 
of two kinds—fermented sugary solution or leaf or 
berry infusion. The former owe their stimulating 
effect to alcohol, the latter to alkaloids. Tea was 
discovered by the Chinese at a time so remote that 
they ascribe to it a supernatural origin. It first came 
to England about 1571, when it was sold for as much 
eee 
