236. American Quarterly Microscopical Journal. 



worthy co-laborer, Dr. Ward, of Troy, whether our i-iooo of 

 an inch, or i-ioo of a millimeter, or any space whatever, that 

 may be adopted as a standard micrometric division, is precisely 

 the quoted fraction of the original standard, although it is de- 

 sirable to have it so if practicable. In our view of the matter, 

 any given space upon a stage micrometer might serve the pur- 

 pose. Micrometric measures are not to be compared to the 

 meter or even the centimeter. They will be expressed in terms 

 of a given unit, and compared together by means of the 

 same unit. The real advantage, therefore, of a standard 

 micrometric division will not be that it is an aliquot part of a 

 larger measure in use. Its value lies in the fact that this par- 

 ticular division has been declared standard by a competent 

 and duly authorized body, and that all standard micrometers 

 must agree with it. It is certainly desirable, for convenience, 

 that it should be an aliquot part of some standard in daily 

 use. We assume, however, and not without reason, that such 

 a subdivision of a given standard is possible, and that the 

 standard for division finally adopted will be the meter. 



The term unit, in this connection, means the smallest whole 

 number used in giving dimensions. Now, when the i-ioo mm. 

 unit was proposed it met with the, perhaps too hasty, approv- 

 al of the Congress, and since then has been subjected to criti- 

 cism on the ground of its being too small for the maker to work 

 from. The intention was not to adopt a unit for the maker of 

 micrometers to subdivide, but rather one which would serve as 

 a basis for the comparison of all future rulings. We are still 

 inclined to the belief, after carefully reviewing the subject,, 

 that the most appropriate division for our standard microm- 

 eter is the I-IOO mm., and for the following reasons : 



1. Assuming the metric system to be adopted, the i-ioo mm. 

 will be the division most frequently in practical use. 



2. A larger division would be seldom employed, and if such 

 a one were adopted, makers could rule these large divisions 

 quite accurately, and leave us no assurance that its sub- 

 divisions were as true as they should be. 



3. A smaller division, as the i-iooo mm., e. g., would be 

 seldom required on stage micrometers. 



Let makers work from any division they may deem it advis- 

 able, whether it be the meter, centimeter, or decimeter, the 

 values we want are the i-io and i-ioo mm., and it is the value 



