Description of a New Compensating Pendulum. 275 



Fi£. 1. 



formity of action in a time-keeper. The arrangement of the parts 



is so simple as to be readily understood by any skillful workman, 



and as it is entirely free for the adoption of any one who may 



prefer its construction, I have prepared a description and diagram 



to render it intelligible. 



Fig. 1, shows the whole pendulum, the 



dotted lines representing similar parts to those 



on the opposite side, and are introduced to 



render the drawing more easily understood ; 



a is a similar spring to that which is attached 



to the pendulum of an ordinary eight-day 



clock, and is firmly attached to the perpen- 

 dicular brass bar 6. Through h there is the 



usual opening for the guy-wire, which gives 



motion to the pendulum. This bar is firmly 



affixed to the transverse bar c either by riv- 

 eting or soldering. On each end of the bar c 



there is attached a brass rod c?, c?, and one inch 



from each of these there is also affixed a steel 



rod e, e. These four rods pass through the bar 



p, which is intended merely to preserve them 



in their proper position, and is attached to the 



two brass rods by a pin passing through both, 

 while the steel rods are allowed to move 

 freely through the holes. At/, a transverse 

 bar or lever is affixed to tZ by a loose pin pass- 

 ing through them, and the same attachment 

 is made to the steel rod e at g. This bar is Jiillil 



four inches long, three inches of which ex- «|fe 



tend from g to h, and a similar one is at- ^lUllii*'^ 



tached to the dotted rod d and extends on ^ 



the opposite side. At h there is another loose attachment to the 

 rod i, which is of steel, and which is again affixed to the bar k. 

 At k there is a permanent bar m, which passes through the weight 

 o, and has the usual adjusting screw n at the bottom. 



Rationale. — Suppose that by an increased temperature of 20°, 

 the steel rods e, e, are expanded in length ^\ of an inch. The 

 rods c?, c?, being of brass, and a small fraction larger than the steel, 

 will expand ^ of an inch by the same increase of temperature, 

 it being an established theory with the best French chemists, 



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