412 EECENT PROGRESS IN PHYSICS. 



a full quotation of later authors, wliicli we had at one time intended, 

 would be in most cases but a repetition of what has already been said. 



The reproduction of works of art by this method has been amply- 

 illustrated in the late European industrial exhibitions. The simplest 

 and lowest application which has, however, had the widest employ- 

 ment is the following : Small figures, generally intended for parlor 

 ornaments, are cast in zinc, and coated externally with copper or 

 some alloy of copper. In this process the electrotype is not properly 

 applied to the reproduction of the figure, but simply to the formation 

 of a copper surface upon a cast already made. Another plan is to 

 precipitate a copper shell upon a fusible metal cast, which is afterwards 

 partly melted out, leaving a very light but sufiiciently solid figure. 

 By these methods the now common "bronze" ornaments are made. 



Fine works are actual reproductions of the surface of a mould by 

 methods already explained, but those requiring more care and atten- 

 tion bear a correspondingly higher value. 



But it is in its applications to printing that this art has had the 

 greatest influence. Detailed descriptions of the mode of operation are 

 wanting, but as to their extent we may form some idea from the state- 

 ment of Lieutenant E. B. Hunt, U. S. A., (in the Report of Professor 

 A. D. Bache, the Superintendent of the United States Coast Survey, 

 for 1854, p. 208, Appendix,) who, in speaking of the capacity of 

 printing from relief, says that "is well illustrated by the 135,000 

 impressions regularly worked from the pages of Harper's Magazine. 

 Each page of this publication is electrotyped, a copper film coating 

 type and wood-cuts alike, and type metal is melted into the back of 

 the copper shell to give it the required thickness ; thus both type 

 and wood-cuts are converted into a relief copper plate, from which the 

 prints are worked off." 



The perfect and certain reproduction on the large scale of the finest 

 specimens of the engraver's art is the most remarkable extension of 

 the electrotype. Of this we have the best account in the anual reports 

 of the United States Coast Survey. 



Electrotype operations of the United States Coast Survey, Mathiot's 

 Improvements. — Although fine copper plate engravings have been 

 multiplied in this manner by the English ordnance survey, by the 

 French " Depot de la Guerre," by the royal establishment at Vienna 

 and elsewhefe, that we are authorized in dwelling upon the methods 

 of our own national establishment is shown by the passage from a 

 letter of Colonel Blondell, director of the " Depot de la Guerre," who 

 says of the account of the operations of the United States Coast 

 Survey : " The perusal of the memoir has convinced me at once of the 

 superiority of the electrotype methods which are used in the United 

 States. The reproduction in less than three days of a plate of large 

 size is an improvement of the highest importance." 



We have drawn our information from the annual reports of the 

 Coast Survey, but have also verified this by personal inspection, under 

 the favor of Professor A. D. Bache, the Superintendent, and of Mr. 

 Georgo Matliiot, who has charge of the electrotype department. 



It should be premised that the maps of this establishment are 

 engraved in the highest style of art attainable under a minute division 



