Mode of ad- 

 justment. 



Ji2() NEW COMPENSATION PENDULUM. 



rled: adding this to one inch, the length of the spring by 

 which the pedulum is suspended, we have three inches of 

 steel; and the expansion of steel to zinc being as 147 to 



147 X 3 



353, we have zz 1'25 inches nearly for this part of the 



correction. 



The deal rod will be about 44*5 inches long; and its 



expansion being to that of zinc as 49 to 353, we have 



49x44*5 



■ - — :i:6*17 inches nearly for the length of zinc neces- 

 000 



sary to counteract the expansion of the deal, which being 

 added to 1*25 inches, before found, gives 7*42 inches for the 

 whole compensation sought. 



The adjustment is effected in the same manner as before 

 described by means of the screw E F, by which the length 

 of the zinc is either increased or diminished; and below the 

 large weight is a smaller one, for the purpose of regulating 

 the pendulum to the greatest nicety. This small weight 

 may have a tube of zinc attached to it, on the same princr* 

 pie as that of the larger, to correct the expansion of the 

 steel screw, if it be thought necessary. 



The chief objection to this pendnlum appears to be, that 

 the compensation is partly enclosed in the weight, and con- 

 sequently is not likely to be so soon affected by any sudden 

 variation of temperature, as it would be if it were exposed 

 to the immediate influence of the atmosphere. But it has 



Its advantages, the advantage of being much shorter, and far more simple 

 in its construction, than the one first described, and is there- 

 fore on the whole perhaps preferable. 



Tberompen- If it be thought more convenient, the compensation may 



sation may be ^yQ divided, and half placed between the weight of the pen- 

 dulum, and the other half on the cock of the time-piece; 

 and the nut for regulating it may be either above or below. 



Advantages of Experiments in regular observatories can alone determine 

 the relative merits of this pendulum; It certainly possesses, 

 the superior advantages of economy, simplicity, and ease of 

 adjustment, and there appears every reason to believe, that 

 it may be found at least equal in point of accumcy to any 

 that has hitherto been described. 



Objection to 



thiricomijensa' 



tion. 



4his pendu' 



lum. 



Exeter, ApriU 1808. 



XI 



