288 PROCEEDINGS OF THE AMERICAN ACADEMY 



subdivisions were investigated, with the following results. A positive 

 sign indicates that the measured space is too short ; a negative sign, 

 that it is too long. 



Subdivisions of the Yard. 



Subdivisions of the Meter. 



10 +.00288 10 —.00016 



These corrections involve the errors of transfer. No attempt was 

 made to determine and apply the corrections due to the curvature of 

 the ways upon which the slide carrying the microscope moves. 



The subdivisions of the centimeter rest upon the authority of a cen- 

 timeter subdivided into 100 equal parts by Brunner Freres, of Paris, 

 for the office of the Coast Survey. By the permission of Professor 

 Hilgard, I have made an extended series of comparisons between this 

 unit and a centimeter derived from the screw of my own dividing en- 

 wine. The comparisons were made by means of the comparator for 

 short lengths, described in the American Microscopical Quarterly for 

 April, 1879. The Brunner scale is divided on silver inlaid in brass. 

 In my own scale, the graduations are upon glass. 



