90 Balances for Delicate Weighing. [Jan. 



screwed down upon the beam securing the fulcrum c, 

 which is further fastened by the bottom end of the upright 

 wire d, entering a hole made to receive it on the upper part 

 of the fulcrum. This prevents side motion, the wire being 

 screwed through the brass a.-— The ends of the beam 

 fig. 65 are tipped with brass, and the point a, slides in 

 a small groove made to receive it, and is secured by 

 the tightening nut b. The thick end of the pointer c is 

 screwed through the end of the brass d, and abuts against 

 the point a^affording the means of adjustment by thrusting 

 the point a, towards the centre of the beam : — e is a tighten- 

 ing nut to make the pointer c, secure.- — A plain piece ofwiri 

 with a screw on it, is used also at the other end of the beaJ^ 

 for the same purpose. — I shall presently state the methoi? 

 I used for adjusting the beam to make it an equipoise. 



11. The scale pans of this balance are suspended by^l® 

 loop, figure 7, where a, is a small steel screw passing throi- — 

 the top of the loop, having a shallow cup or dishing at the 

 bottom to prevent its sliding off the point, which with e of 

 end of the beam is shewn inside the loop. This small g, is 

 cavity is finely polished, and is intended by being contPce 

 simply to secure the loop from wandering, or slipping off i 

 point but it does not at all interfere with the delicacy or 

 sensibility of the balance, which it might do were it not 

 carefully formed, and made as shallow as possible with re- 

 ference to the use required. The wire bent into the figure 

 of an 8 v/ith the three lines attached to it represent the man- 

 ner in which the scale pans are secured, the lines being 

 merely silk thread. — This balance is a very good instrument, 

 and its indications are satisfactory and may be depended on 

 with from 100 to 200 grains in each scale to the too% oo^th 

 part of the weight. 



12. To make this balance an equipoise I proceeded thus. 

 I adjusted the points in the beam as nearly as I possibly 

 could to equidistances from the fulcrum, and then made the 

 beam balance, or point to nonius on the index. — The scale 

 pans with the loops complete were then made perfectly equal 

 in weight. They were then attached to the beam and two 

 perfectly equal v/eights of 100 grains each were put into the 

 pans, one in each pan, and the balance tried. The end that 



