PHYSICAL ASTRONOMY. %4tS 



The siderial revolution of the Moon is 27a.32166, 

 124. and her mean distance 59.879 semidiame- 

 ters of the Earth. From this, on the supposition 

 that the squares of the periodic times are as the 

 cubes of the distances, the period of a body pro- 

 jected, so as to describe a circle round the Earth, 

 will be found l h .41516. From this the arch 

 which the body describes in one second, is found 

 to be 4/.13".48'"; and the deflection from the 

 tangent in one second, if reduced to feet, comes 

 out 16 and a small fraction, the same with the 

 descent of a heavy body in one second, at the 

 surface of the Earth. 



NEWTONI Princip. lib. in. prop. 4. 



On the subject of this section, see NEWTONI Priricip 



Math. lib. ImuSj sectio 2da, 3tia, 7ma, 8va, lima. 



JOH. BERNOUILLI, Opera> torn. ImuSj NO. 86. 



EULERI Mechanica, torn. i. cap. 5tum. Particularly 

 prop. 80, 81. 



FRISII Opera, torn. Stius, Cosmographia, lib. Imiw. 



Dr MATHEW STEWART, Tracts Phys. fy Math. 

 Tract 1. The subject is there treated in a man* 

 ner strictly geometrical. 



LA BANDE, liv. 2de, torn. m. 

 VINCE, Astron. chap. 31. vol. u. 



Theorie des Mouvemens des Planetcs, par M. LA 

 PLACE, lrep ar tie, Paris, 1784. 



SECT. 



