102 SEC. 3. MEASUREMENT. 



491. Ancient Striking Clock. 



Lent from the Patent Office Museum by the Commissioners 

 of Patents. 



This clock is of Swiss manufacture, and supposed to have been made in the 

 year 1348. It was obtained from Dover Castle, and had never been removed 

 from there till the year 1872. It is interesting from the fact of its having the 

 verge escapement, which was used many years before the pendulum. 



49 la. Very curious Timepiece, apparently designed by 

 Mudge. E. Dent. 



The escapement is a true remoutoire ; two small pendulum springs are 

 wound up at every beat of the scape wheel, and these give impulse to the 

 balance. The balance is controlled by two pendulum springs, one above and 

 the other beneath it ; the first of these receives the action of the " compen- 

 " sation curb," the second is for ordinary regulation. The action of the 

 " compensation curb " is analogous to the ordinary regulation by curb pins, 

 but the curb pins are advanced backwards or forwards along the spring by 

 the operation of the compensation pieces, which, being constructed of brass 

 melted upon steel, bend at every change of temperature. The whole time- 

 piece has been designed and got up with a surprising degree of refinement. 



492. Working Model of Chronometer Escapement, with 

 two inch scape wheel. Philip John Butler. 



493. A Small Electric Pendulum. Striking seconds 

 on a bell, and thus capable of being used for astronomical studies. 



Antoine Joseph Gerard, Liege. 



494. Book containing plans of instruments, apparatus, and 

 machines. Antoine Joseph Gerard, Liege. 



49 9a. Chronometrical Regulator, for putting in motion a 

 registering cylinder. Mr. Yvon Villarceau. 



This system of regulator, the theory of which is due to Mr. Yvon Villarceau, 

 is represented by the model included among the objects exhibited by M. L. 

 Breguet. 



500. Edelmann's Seconds Pendulum, with galvanic 

 attachment. M. Th. Edelmann, Munich. 



501. Curonometric Comparateur, an instrument of coinci- 

 dences, for determining the difference of time between two distant 

 clocks. M. Redier. 



5Ola. Collection of Steel and Electro-gilded Pendu- 

 lum Springs. E. Dent. 



502. Clock employed in the Pantheon Experiment by M. L. 

 Foucault. Conservatoire des Arts et Metiers, Paris. 



502a. Different applications of Metal Tubes of ellipsoidal 

 section to instruments for measuring pressure, temperature, 

 weight, speed, and time. 



