SOLAR CHRONOMETER. 



5G3 



a small one, it will be sufficient to place the stand upon an ordinary table, 

 without verifying the horizontal plane. With a large globe the arrangement 

 must be very exact. 



A SOLAR CHRONOMETER. 



M. Flechet's chronometer, of which we ( give an illustration, is a kind 

 of equitorial reduced to its most simple form. It is possible to ascertain 

 the exact time by it very easily. It consists of a disc, A B, divided into 

 twenty-four hours and fractions of hours. This disc turns upon itself 



Fig. 635. Solar chronometer 



around an arc, CD, which has a direction parallel to the axis of the world, 

 and can be moved on a joint, E, according to the latitude of the place ; 

 F is a lens which can be moved and presented to the sun at any time, 

 forming the centre of a concave and exactly spherical plate represented 

 at GH. 



When the instrument is fixed so that the axis, c D, is parallel to the 

 axis of the globe, the disc, AB, is turned so that the centre of the image of 

 the sun, produced by the lens, shall fall at ;;/. The real time is found by 

 an examination of the position of the index, A, upon the hour graduations 

 of the disc. A French writer, Ch. Delounay, has mentioned this instrument, 

 and considers it easy of arrangement, exact in time, and very useful. 



