48 American Quarterly Microscopical Journal. 



No action seems to have been taken in the matter at that 

 time or since. 



We are as far from a deiinite standard to-day as we ever 

 were, and unless the question is taken up in good earnest by 

 able and well-known men, representing in some way the micro- 

 scopists of the countr)^ either as delegates from societies to a 

 convention like this or at a special meeting for the purpose, it 

 will be as it is now for years to come. 



If we pretend to scientific accuracy in our work we must 

 have reliable micrometers; and, if we desire to avoid trouble in 

 reading the results of the labor of others we must all use the 

 same unit of measurement. 



If well chosen, our standard will be adopted by other 

 countries, and we have a good opportunity now to make 

 this congress remembered in the history of our science. 



To secure our standard, Prof. Rogers promises to place in 

 the hands of a properly appointed committee, representing five 

 of the leading microscopical societies of the country, six 

 standards consisting of fifty spaces, covering exactly ^V part of 

 the standard British yard at Washington. Each of these 

 spaces would be divided into 10 equal parts, thus giving 500 

 lines. These lines would be i-ioooth of an inch apart. Prof. 

 Rogers then goes on to say as follows: 



"This committee shall ascertain tnat these six micrometers 

 are comparable within certain very narrow limits. I will then 

 present one to the properly appointed custodian of each 

 society, and retain one for myself. I can then at any time make 

 duplicates of a common standard." 



I should add that Prof. Rogers is now having a new machine 

 made, which he has reason to believe will enable him to do 

 better work than the one he is now using. Even with the one 

 he now has, he can arrive very near the truth. 



Some of his earlier micrometers are not reliable, and all 

 made previous to May, 1877, belong to this class. The errors 

 of these range from zero up to 1-7000 of an inch. 



By perfecting his machinery in various ways, this error has 

 gradually been made less, until it became about 1-40000 of an 

 inch in maximum; but a few weeks ago even this residual error 

 was accounted for, so that now. Prof. Rogers believes he can 

 rule one hundred micrometers just alike. 



