g08 Tmansactions of the American Inbtitute. 



minute, but have beem very generally discarded as a useless append- 

 age. 



The hobby of compensation has been ridden until seemingly un- 

 able to go one step farther. Almost every ingenious mechanic in tho 

 past two hundred years has been astride of the animal, and though 

 great results have been attained in chronometer balances, still we 

 seem to be a long way from the end of our journey in search of a 

 perfectly compensating pendulum. I do not think that one in fifty 

 of our mercurial pendulums are compensating. I did hear of one 

 some time since. A gentleman was in town from an obscure vil- 

 lage in Pennsylvania, and in the course of a conversation, began 

 telling me of a wonderful clock he had in his store, which, he said 

 had not varied fifteen seconds in twelve months from the standard 

 tune. Cold nor heat did not affect it in the least. Being somewhat 

 jealous of country time, I felt disposed to argue the matter with 

 him, but it was no use, he had me on all points. Just as I was 

 jibout givmg up in despair it occurred to me to ask him if he took 

 his own observations ? "Oh! yes, certainly," he answered, "I have 

 si noon mark cut in the floor." 



Mr. Hotchkiss filled an order some time since for a clock with a 

 mercurial pendulum, the jar of which held one hundred pounds 

 of mercury. I cannot say how well it compensated, for in a few 

 weeks the jar got broke by accident, and the mercury lost. The 

 owner did not despair, but ordered a new one. 



Experiments have been made, and rules laid down for the exact 

 weight of rod and stirrups, that a given column of mercury will 

 compensate, yet no one seems to heed them. The stirrup in par- 

 ticular is designed more for show than compensation. 



We can put a chronometer in a refrigerator, and run it forty-eight 

 hours, and then in a hot bath for forty-eight more, and we very 

 soon get at its adjustment; but with the mercurial or any pendulum, 

 diflSculties step in. In a regulator we can put lamps in the case, 

 and heat it up in that way, and then open the doors and windows 

 below zero, but I think them imperfect tests, particularly the heat- 

 ing. 



The tower pendulum we can only adjust by watching in the heat 

 of summer and cold of winter, and if we are very observing, and 

 live to a good old age, we may get it adjusted. 



I am well satisfied that if the City Hall clock had a wood rod, 

 -well seasoned and well varnished, and a very short pendulum spring, 

 it would run at a better rate than now. We have, with the English, 



