}28 SEC. 3. MEASUKEMENT. 



Ji 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. 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. Chronometric 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 and Co. 



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

 Foucault. Conservatoire des Arts et Metiers, Paris. 



502a. Different applications of Metal Tubes of elliptical 

 section to instruments for measuring pressure, temperature, 

 weight, speed, and time. 



1. Manometer for steam, air, or water pressure. 



2. Barometer. Counterpoised barometer. 



3. Thermometer. 



4. Tacheometer, or speed indicator. 



5. Balance for light and heavy weights. 



6. Clock with pneumatic motor. 



M. Eugene Bourdon, Paris. 



502 a. Motor Clock and case, with two electric dials, 

 batteries, and fittings. T. Cooke $ Sons. 



503. Electric Apparatus by M. Foucault, for keeping up 

 continuously the motion of the clock. 



Conservatoire des Arts et Metiers, Paris. 



