850 TRANSACTIONS OF THE AMERICAN INSTITDTE. 



Waste of Coins. 



The life of coins is said to be much briefer now than before the 

 introduction of steam for passenger travel. The real cause of the 

 increase of wear in Europe probably arises from the fact that coins 

 are not saved and secreted as they were formerly. Now they are 

 subjected to constant attrition by being carried in pockets and 

 passed from hand to hand. On the average one hundred old 

 English shillings would not make juore than eighty new ones. 



The mode of manufacturing coins is opposed to their longevity. 

 The plain disk of metal is very soft when placed between the dies. 

 Compression hardens the recessed surfaces, while the raised sur- 

 faces are left in a state very near their original softness. Unfor- 

 tunately, the raised portions of the coin are just those'' most 

 exposed to attrition. It has been proposed to raise the rim of the 

 coin so as to protect the figures within. This plan might make 

 the denomination of the coin legible for a longer time, but would 

 not diminish the actual wear. Our copper and nickel coins never 

 bear the intrinsic value they represent, so that there is really but 

 a trifling loss by attrition. Gold and silver coins, on the contrary, 

 are originally worth their nominal value, and any plan to better 

 protect them from wear, when they again come, into general use 

 in this country, should be favorably entertained by the general 

 government. 



Cameras. 

 M. Carey Lea, of Philadelphia, says American cameras are usu- 

 ally made of wood, a material liable to great objections — the most 

 prominent being the warping it undergoes in our changeable cli- 

 mate. He has seldom found one absolutely correct in its construc- 

 tion. An important requisite in a camera is that the sensitive 

 plate should be exactly perpendicular as to the optic axis of the 

 lens, otherwise, while one side of the plate is in true focus, the 

 other will not be strictly so. On a cursory observation the whole 

 may appear to be in tolerably good focus, but a careful examina- 

 tion with a glass will verify the difference. In English made cam- 

 eras the focusing-screen and dark side usually slip into a groove, 

 while in those of American manufacture dowels are fastened into 

 the bottom of the camera, and fit into holes in the slides, which 

 close up by a spring-catch at the top. The latter plan is liable to 

 become loose and unrelial)le by wear. Another fault is the allow- 

 ing of too much play in the rack and pinion by which distance is 



