RECENT PROGRESS IN PHYSICS. 415 



more than three or four ounces to the square foot. These being cut in 

 any required form with a pair of scissors, require merely to be cemented, 

 each in its proper place, on a blank plate coated thinly with shoe- 

 makers' wax." The facility of combination thus introduced has 

 greatly abridged the time and labor expended upon this species of 

 work. — (Coast {Survey Report of 1855.) 



A still further extension of this idea is noticed in the Coast Survey 

 Eeport of 1857, p. 189. " It is now practically ascertained that thin 

 electrotypes are all that is necessary; the stiffness requisite to print 

 from being given by stretching them on steel plates having a smooth 

 surface and cut to the proper size." Mr. Mathiot also adds as follows : 

 *' The working of the thin electrotypes has suggested to me the idea 

 of using these plates on a circular bed or roller, and gaining thereby 

 the great advantage of cylinder printing for flat plates." The im- 

 provement of copper plate printing by steam machinery is thus sug- 

 gested as highly probable. — G. C. S.] 



