200 COMPENSATION PENDULUM, 



drawing which accompanies it, I believe it to be new, and 

 wishing it to be useful to the world, I have presumed tq 

 send it to the Society. I am, sir. 



Your humble servant, 



ADAM REID. 

 Reference to the Drawing of Mr, Reid's Compensation 

 Penduluniy PL VI. 

 Thependulum Fig. 1 and 9, PI. VI, AB represent the steel rod extend- 

 **"' • ing through the whole. C the bob, supported upon the 

 compensating cylinder of zinc D, wiiich surrounds the rod 

 AB, and rests upon the nut E of a screw tapped upon the 

 end of the steel rod, to bring it to exact time ; as this ex-? 

 pands downwards by heat, the zinc expands upwards the 

 game quantity ; so that the bob always remains at the same 

 distance from the point of suspension. Fig. <2, is a section 

 to explain more clearly the thickness of the zinc tube D, 

 and the form of the steel rod at a, where it passes through 

 the bob, which is of the shape shown at L, that the rod or 

 the bob ptiay not turn round, when the nut E is turned Iq 

 adjust it to time. 



The following Method is to he employed to make the Compen* 

 sating Pendulum of Steel and Zinc. 



Method of Procure a rod of forged blister-steel 52*7 inches long, '27 



saajcingit. diameter, heat it to a white heat, which will open the pores 

 of the steel, and give it the smallest expansive power, that 

 Steel pf this texture is possessed pf. V^hen cold straighten 

 it with a mallet of wood on a wooden block, that no part 

 may be condensed partially; which would be the cj^se, if a 

 hammer and anvil were used. Then cast a solid rod of zinc 

 12"5 inches long, '68 diameter, with the lowest heat, that 

 "^ill fuse it; and pour it into a metal mould. This will giye 

 it the greatest density, consequently the greatest expansion, 

 that zinc is possessed of. Then bore a hole through the 

 centre of it longitudinally, that it may move freely on the 

 steel rod, which has a nut and screw at the bottom end to 

 regulate the clock to time ; the bob, as shown in the en- 

 graving, rests on the upper end of the cylinder of zinc, and 

 will continue in the same place, whatever expansion or con- 

 traction takes place, Jfthe adjustment be correct. 



