195 ACTION OF HEAT MODIFIED 



to be removed, oil, or tallow, at a temperature sufficiently high to reduce 

 them to the metallic state, so that they may be used in sub- 

 sequent operations." 

 The matiipula- Nothing more remains but the mechanical process, which 

 tion easy. jg ^^^^^ ^^^ f^^. ^^jj^h we must refer to the Bulletin of the So- 



ciete d' Encouragement already quoted. This Bulletin should 

 be consulted by all who would know the minutiae of the art. 

 Fidelity of the We shall conclude by observing, that the fidelity of the im- 

 process. pressions or stamps (cliches) is so great, as to give with the 



greatest accuracy every ramification in a rose leaf. 



During the fabrication of assignats, they were stamped both 

 by the hand and by engines. Like all other useful processes, 

 this was soon improved in consequence of the necessity of re- 

 peating it. The operation is rendered more expeditious and 

 The stairi-Mng more exact by means of a simple machine. A plate added to 



pel-formed by a ^j^^ ^f j^j_ Darcet, and engraved in the Bulletin of the 



SH»:p.e ma- ' '^ ' . 



chiiie. Societe d' Fncovrageinenty represents this machine which is des- 



cribed in M. Darcet's paper. 



To this abstract were subjoined some impressions taken with 

 plaster of Paris from wooden cuts of M. Duplat, and then 

 worked off from stamps made with M. Darcet's compound 

 metal.* 



IV. 



Account of a series of Experiments,, shewing the Effects of 

 Compression in modifying the Effects of Heat. Br/ Sir 

 James Hall, Bart. F.R.S. Edinburgh. 



(Continued from page 128.J 



Sect. viri. — Eormation of Coal. — Accidental occurrence 

 which led me to undertake these Experhnents. — Results ex- 

 tracted from a former publication. — Explanation of some 



* The prints in Za Kevue exactly resemble wood-cuts. The 

 press-work not being performed in a better manner than common. 

 it is not possible to form any judgment of the minute differences. 



difji' 



