374 POPULAR LECTURES AND ADDRESSES. 



or metal support, attached to a stone pier, such as 

 those used by astronomers for bearing their optical 

 instruments. There can be little doubt but that 

 the use of this simple precaution, and the making 

 the pendulum many times heavier than hitherto, 

 might render the performances of an astronomical 

 clock, even with a Graham's dead-beat escape- 

 ment, not merely two or three times better 

 than those of a good watch carried about in the 

 pocket, but ten or twenty times better, which wt* 

 might well expect it to be in its immensely more 

 advantageous circumstances. A good marine 

 chronometer is probably little less accurate than 

 the best astronomical clocks of the present day. 

 It seems strange that such a very great improve- 

 ment on Graham's clcacl-bcat escapement as cither 

 the chronometer escapement or the detached lever 

 constitutes, should not yet have been applied to 

 the astronomical clock. 



An interesting illustration of the influence of 

 the different modes of suspension on the rate of 

 a chronometer is had by suspending bifilarly a 

 marine chronometer or a good pocket-watch. For 



