Amstutz Optical Micrometer. By M. I). Ewell. 159 



are being furnished for different trades. For instance, for photo- 

 engravers an " E^ " scale is made having two groups of fine lines 

 at 0-002" (500 per in.), separated from each other Jg in. so as to 

 make it relatively easy to count any uniform divisions or screen- 

 lines. Outside of and between the groups the main divisions are 

 Y^Q in., and indicated in fives for convenience of counting. Among 

 other scales, some are ruled in metric dimensions, the smallest 

 divisions usually being ^ mm. It is a remarkable convenience 

 to be able to make definite lineal measurements in this manner of 

 microscopic objects. There is no trouble whatever to estimate the 

 j^Q-Qth part of an inch by means of the finest inch divisions, as it 

 simply involves dividing one of the spaces into two parts. The 

 sizes of half-tone dots can readily be determined. These glasses 

 are being made at Valparaiso, Indiana, U.S., where Mr. Amstutz's 

 son, F. W. Amstutz, is associated in their manufacture. 



