Effects of the Orbicular and Rotary Motions of the Earth. 435 



heavy ones will be forced towards the centre hy their mutual col- 

 lisions. Such will be the law, governiiis,^ all the masses that are 

 free, to move one among another, as the fluid parts and the 

 moving or moveable parts. It is a law growing out of the con- 

 ditions, and the conditions are those whicdi exist in Nature. If 

 a projectile, therefore, have a specific density equal to the air or 

 fluid into which it has risen, it will be carried round tiie earth in 

 the concentric circle of that stratum, because the momenta are 

 there equal : but, if it be lighter than the air, it will then be re- 

 flected by the donser strata, till its own momentum, and the mo- 

 menta of the surrounding air, be equal ; while, on the other 

 hand, if it be heavier than the circumambient air or fluid, then 

 the air or flnid will rise over it and deflect it to the earthy with a 

 force which will be nearly in the ratio of their densities. 



Galileo was the first geometrician who analysed the phseno- 

 mena of falling bodies, and determined the law of their motions. 

 He was followed in this theory by Newton, and his doctrines are 

 justly respected to this day. That great man considered, how- 

 ever, that bodies thrown perpendicularly upward, merely describe 

 in rising and falling the same straight line. He was one of the 

 most powerful advocates of tlie two-fold motions of the earth ; 

 yet he never considered bodies acted upon by a temporary and 

 relative projectile force, as still subject to the absolute two-fold 

 motions of the earth and atmosphere. Hence he considered the 

 force which returned the body to the earth, as equal in small di- 

 stances to the weight of the body, and as acting in right lines 

 from the centre of the earth. In this notion he vvas borne out 

 bv the belief in all kinds of sympathies and emanations which 

 characterized Ids age, as well as tiiat of Newton ; and to these 

 superstitions may, doubtless, be referred the doctrine of an ema- 

 nating gravity. It appears, however, that, as a body subject to 

 the novel force of an upright projectile, does not, in truth^ de- 

 scribe a perpendicular line, but two sides of an exceedingly obtuse 

 triangle ; no force is requisite to deflect it to the earth, but the 

 exceeduigly small one which creates the nascent deflection. 

 Hence, as the angle of deflection required to carry a body through 

 the first inch, is not the 200()dth part of a degree; the deflective 

 force need not be more than the 120,000dtli part of the perma- 

 nent momentum of the body created by the orbicular force: and 

 consequcntlv no difficulty arises in referring the small deflective 

 force to the combinations of the great motions of our planet. 



E e 2 Suppose 



