62 Mechanical Philosophy. 



tingen, and by Dr. Herschel, of Great-Britain; 

 who, by the aid of very powerful and accurate in- 

 struments, and with the skill and perseverance for 

 which they are so eminently distinguished, have 

 made surprizing progress in investigating this de- 

 partment of the lunar phenomena. 



When Newton died, several of the inequalities 

 of the planetary motions, arising from the disturb- 

 ing forces of various bodies, were with difficulty 

 reconciled with the astronomical principles which 

 he had laid down. These inequalities have been 

 successively investigated since that time, their 

 causes ascertained, their laws fixed, their perfect 

 consistency with the Newtonian theory demon- 

 strated, and thus a very formidable objection to 

 that theory satisfactorily removed. — It is known to 

 mathematicians, that this celebrated philosopher, 

 calculating the effect of the sun's force, in pro- 

 ducing the precession of the equinoxes, fell into 

 an error, and made it less, by one half, than the 

 truth. The true quantity of this motion was first 

 determined by M. D'Alembert, in 1749; who 

 also, in the course of his inquiries, more fully ex- 

 plained the nutation of the eartJis axis, which 

 had been discovered a few years before by Dr. 

 Bradley. With no less diligence the inequalities 

 in the revolutions of all the planets, and especially 

 of Jupiter and Saturn, have been examined, as- 

 certained, and reduced to regular principles. In 

 these difficult investigations, many astronomers 

 have employed themselves, in the course of the last 

 century, and by their labours rendered important 

 services to this science; but, perhaps, none of the 

 number deserve more honourable distinction than 

 Euler, De la Place, and De la Grange, whose 

 accurate observations, and rigid and delicate ana- 

 lyses, with a YiQW to explore the anomalies in 



