404 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



mercury is moved upward. The compound rod is usually made with zinc 

 and iron alternately riveted together at their ends. Two rods of iron act- 

 ing downward and one rod of zinc upward, provided the expansion of the 

 zinc was double that of the iron, would equalize this action by heat and 

 cold. 



The manner and methods of making watches have so improved within 

 the last 25 years that their cost has been materially reduced, and the divi- 

 sions of time have been carried to quarter seconds with great exactness. 

 Such time-pieces have had the effect of making all our calculations of time 

 more close and exact. Now we state the time of a race to the parts of a 

 second. This exactness of measurement, by means of the electric tele- 

 graph, was first used and with complete success in astronomical opera- 

 tions, by the late Dr. Locke, of Cincinnati. The late lamented Brig*. Gen. 

 Mitchell, many will recollect, lectured in this city on this subject, and 

 explained what he called the personal equation, it having been found that 

 the time of seeing and recording, or in other words the time of the passage 

 of thought from the brain to the hand, was not the same in any two per- 

 sons. This subject of Horology has not yet been fairly and fully discussed 

 in this country, and I hope we will continue it till we are thoroughly 

 acquainted with what has been done. Over 100 different escapements 

 have been invented and used in clocks and watches; and this topic alone 

 would interest an audience an entire evening. 



Prof. Everett. — I have seen it stated that the American watches are 

 made with a more powerful spring; so much so, that they are liable to 

 wear out very soon; and that the pcnver of tlie spring covers up any fault 

 that may be in the watch. I would inquire if this is so ? 



Mr. Bradley. — The springs of American watches are no stronger than 

 those of foreign watches. The main-springs are all alike as regards 

 strength. 



Mr. I. G. Chislom. — As American watches are made without the fusee 

 and chain, I would like to inquii-e in what way the unequal pressure of 

 this spring is overcome? 



Mr. Bradley. — It was supposed that this could not be done without the 

 fusee and chain, and the English still adhere to this opinion; but experi- 

 ence has proved that watches can be made to run with regularity without 

 the fusee, and this is done by a very quick movement. It will be observed 

 that the balance wheel in these watches moves very fast; the American 

 watches, with no fusee, drum or chain, has fewer parts, less friction, and 

 is not so likely to get out of order as the European, and when broken can 

 be more easily repaired. 



Mr. J. Dixon. — There was a very curious clock made in 1822 and 1823, 

 by Harrison G. Dyer, now I believe of this city. He made several of these 

 clocks, some with one wheel, others with two. The one wheel clock, with 

 one winding, would run one day, and that with two wheels, eight days; 

 and he made one that would run a year. Mr. Bogardus, a member of this 

 Institute, made a clock which has been running twenty-five years; it has 

 but three wheels, and during all this time has been oiled but once. 



The Chairman. — It is very interesting to look over the accounts of the 

 various movements that have been invented for recording time. That of 



