IT. LENGTH. 



The arrangement of the apparatus is as follows : 



In a solid brass pedestal, which rests on three adjusting screws, there is 

 cemented a strong glass tube a, 1% meter long, to which two brass bars b are 

 affixed. Each of these brass bars consists of two parts, of which the one 

 moves or slides in the other in such a manner that it can be either lengthened 

 or shortened. The screw c serves for fixing the chosen length. By means 

 of the joint d a horizontal rotatory or veering movement of the fore-part of the 

 bar can be effected. Close to its free end there is on each side a steel point 

 the two forming together an axis which is held by a bow// carrying two 

 pans, in such a manner that the bow can be easily but surely turned round 

 this axis. 



The lever gg which must be firmly connected with the bow, has longitu- 

 dinally a slit, or slide, with two sliding pegs placed in a level position with 

 the axis and fastened to the bow, along which the lever can be moved, so that 

 at whatever distance from the axis the extreme end of the lever may be fixed 

 the lever must always turn with the bow around the axis. 



In order not to be obliged to take the measurement of the length of the 

 lever afresh at each experiment, the lever is provided at its upper surface 

 with conical-shaped cavities in which the screws hk catch. These conical- 

 shaped cavities would be, properly speaking, visible only in a drawing of a 



