OF ARTS AND SCIENCES. 317 



(1.) AflJHstment of the standards T, C. S., R^, and R,, upon sup- 

 ports at their neutral points, upon the table S^ The defining lines at 

 one end were placed nearly over the fulcrum at the left end of the 

 carriage. T, having the least mass, is placed in front. 



(2.) Permanent adjustment of the microscope plate I at a con- 

 venient distance from the end of the frame L. 



(3.) Rapid movement of the carriage S by the handle D, until the 

 right defining line of the meter T is, brought nearly under the micro- 

 scope M^ 



(4.) Movement of the plate K by the hand-wheel R, until the de- 

 fining lines at the opposite end of T'are brought into the field of the 

 microscope M. 



(5.) Adjustment of the left-hand defining line under the micrometer 

 of the microscope M, by the horizontal movement of the slide S^ and 

 by the vertical movement S^, and finally by the movement of transla- 

 tion through the lever S^. The first two of these movements are 

 made with sufficient exactness by the coarse adjustment. The defining 

 line of the standard liavinw been brought into coincidence with the 

 fixed line of the micrometer of M by the fine adjustment S^ no fur- 

 ther change is made in the positions of K and I. 



(6.) The adjustment of the right defining line by the motion of 

 the micrometer of M\ by the lever S^ and by the vertical screw S^. 

 These adjustments will disturb the adjustment xinder M only in a 

 slight degree. Usually, however, a second series of adjustments is 

 necessary. 



(7). The length of T' having thus been transferred to the micro- 

 scopes M, M\ the standard C. S. is then brought into position by the 

 slides S^ and the adjustments described above are repeated. The left 

 defining line being coincident with the fixed wire of M, the difference 

 in the length of the two standards is measured by means of the 

 micrometer of M^ An increasing reading of the micrometer- head 

 corresponds to an increase of length. 



(8.) Comparison of the meters R^ and R., in a similar manner. 



(9.) Adjustment of the defining line of the yard of C. S. under M^ 

 by a rapid movement of the carriage S through the hand-lever D. 



(10.) Movement of the plate K till the left defining line of the 

 yard falls under the microscope M. 



(11.) Repetition of the various adjustments and measures described 

 above. 



The average time required to make these adjustments, and to take 

 four readings of M^ for the defining lines T^', T''\ for each edge of 



