406 T. A. Jag gar ^ Jr. — Microsclerometer, for 



focus levelling in the ball-and-socket clip,* followed by rota- 

 tion after centering the point to the cross-hairs : the angle in 

 each of the three faces was found to be 62° — showing that 

 each face is not a perfect equilateral triangle but possesses a 

 slight bulge or rounding. 



Apparatus for rotating. — To the upper end of the shaft, q, 

 is attached a larger pulley, P : the shaft may be raised or low- 

 ered freely in the lower sleeve with the rest of the apparatus. 

 The pulley, p„ on the diamond spindle, is connected by a fine 

 silk belt with p : the tension of the belt is prevented from 

 interfering with the action of the balance by two small pulleys, 

 jPzi Pv rotating within the beam exactly in the pivot axis, and 

 separated by a distance equal to the diameter of p 2 . The belt 

 tension from without is thus applied to the balance system in 

 its axis of rotation, and thus only has the effect of adding to 

 the sensitiveness of the balance by assuming a portion of the 

 weight which otherwise would rest wholly on the pivot bear- 

 ings. Torsional strains are obviated by the parallelism of the 

 two portions of the belt between^ and j? 2 , and^> 4 and^> 2 . 



Apparatus for recording rotations. — The rotations of the 

 diamond spindle are reduced 1/60 by two pinions and two 

 gear wheels of the ordinary watch pattern. Over the second 

 gear is a dial divided into sixtieths : the spindle from this 

 wheel passes through a sleeve in a brass indicator plate, i, 

 which acts as a hand : in this a steel spring, z, presses on the 

 spindle, forming a friction bearing. The outer border of this 

 plate carries a crown milling, against which presses the bent 

 extremity of the spring lever, I. When I is pressed down it 

 engages with the milled edge and the spindle rotates within 

 the sleeve without rotating the indicator, */ when lis released, 

 the tension of the spring, z, on the spindle is sufficient to 

 cause this to rotate i, and each division of the dial indicates 

 one complete revolution of the diamond. A graduated toothed 

 wheel, i v is rotated intermittently on each complete rotation of 

 i by the latter's index arm, recording the sixties up to fifteen 

 revolutions — making a total of 900 revolutions of the diamond 

 possible without renewed observations. 



Apparatus for locking and releasing. — The locking appa- 

 ratus affects the balance and the recording apparatus simultane- 

 ously. A half rotation of L causes an eccentric, 0, to press 

 upon the bar, b, above the counterpoise, and at the same time 

 to press down the spring lever, Z, and thus check the indicator, 

 i. The adjustment of the lock is regulated by the thumb- 

 screws, Jc, which limit the rotation of L by checking an angle- 

 piece attached to the L shaft. 



*See this Journal, III, 1897, p. 129. 



