NEW COMPENSATION PENDULUM. glQ 



A piece of iron, is forged one foot long, half of which is This compen- 

 tnade of the same size as the zinc tube is externnlli/, anrj the ?^*l°" descnb* 

 remainder of the same dimensions as the jipper part of the 

 pendulum rod. This iron being placed between the plates 

 of brass, which form the weight of the pendulum, the lead 

 is cast around it, and the iron is afterward forced out, leaving 

 a receptacle for the tube of zinc, which extends exactly to 

 the centre of the weight. 



The brass plate at the back of the weight of the pendu- 

 lum being taken off, a square opening (t}je upper part of 

 which is in a line with the centre of the weight,) is cut 

 through the lead into the receptacle for the tube of zinc; 

 and the tube having been made to slide with perfect freedom, 

 yet without any shake in the receptacle, it is passed upas far 

 as it will go; and marks being made opposite the groves a, b, 

 fig. 3, as represented at fig. 4, corresponding groves are made 

 in the lead with a gouge of the proper size, into which a 

 small quantity of melted lead being poured, the tube of 

 zinc remains firmly secured, and of course can expand in no 

 other direction than from the centre of the weight down- 

 wards. 



In order to restore the lead, which was taken away in 

 making the square opening; a piece of card paper is cut so 

 as to cover the zinc, and the opening may then be filled with 

 melted lead (being careful that it is not too hot,) v/ithout 

 any danger of its uniting with the tube : the back plate of 

 the pendulum weight is then to be replaced and rivetted. 



To the lower end of the pendulum rod a cap of brass is 

 firmly fixed, from the bottom of which a strong steel screMr 

 proceeds, which passing through the hole in the crylinder of 

 zinc, the weight is supported, and the pendulum regulated, 

 by a nut in the usual manner ; and a small octagonal plate 

 of brass is soldered to the bottom of the cylinder, to prevent 

 the nut from injuring the zinc, as well as to divide each re- 

 volution of the screw into eight equal parts. 



To determinethe length of zinc required fora compensation Determination 

 of this form, that part of the steel screw included between <>^^^^ '^"S'^». 

 the nut and the end ot the deal rod must be considered. comi>ensaii6n. 

 This we will suppose to be two inches, which will leave half 

 an inch; by which the length of the pendulum may be va- 

 ried : 



