The Philosophical Enquirer No. XXI. 



210 



out of sleep, that they are perfectly 

 well, but as soon as awake, although 

 the position may not be at all changed, 

 they begin again to rebel against the 

 circumstances in wliich they are placed, 

 in which their stomach speedily co- 

 operates. My principal reason for 

 making this communication, is a hope 

 that it may be the means of preventing 

 to some the exceeding great misery of 

 sea-sickness, for although I do not by 

 experience know its extent, yet, (hat 

 must certainly be extreme suffering 

 which can induce a wish, as it has done 

 in many instances, to be throvvn over- 

 board rather than endui-e it ; and I 

 would tlierefore subjoin a few minor 

 precautions. 



1st. As tlie scat of the affection ap- 

 pears to be iu the organs of digestion, 

 a small quantity of neat brandy sliould 

 be taken as a stimulus whenever a dis- 

 position to qualmishness appears. 



2nd, Keep on deck, and to windward 

 as much as possible, 



3rd. By no means sit down in the 

 cabin, particularly of a crowded packet, 

 for there not only tlie closeness of the 

 air and the sickness of the other pas- 

 sengers are alone likely enough to 

 turn a squeamish stomach ; but the 

 motion of the vessel will be found to 

 affect the suft'erer in a greater degree 

 than in any other situation in tlie vessel. 

 4th. Eat little, but often; the ex- 

 tremes of a full and empty stomach are 

 equally to be avoided : but, above all, 

 go with the vessel, when she descends a 

 wave, descend with her, and when she 

 rises again rise with her, as if you en- 

 joyed the motion. C. F. H, 

 Brisfol, Jan. Qrtfh. 1R21. 

 ♦ 



For the MnnfMy ATagmiue. 



ThePHILOSOI'HICALENQUIRER. 



No. XXI. 



On the TRUE CAUSES of the ELLIPTI- 

 CAL MOTIONS of the PLANETS. 



SINCE Kepler, determined by the 

 analysis of Tyclio's Observations 

 on Mars, that the planets move in ellip- 

 tic orbits, and describe equal areas in 

 equal times, philosopliers have puzzled 

 themselves witli conjectures to account 

 for an irregularity incompatible with 

 the laws of mechanics, which. Avhile the 

 circumstances of their agents and pa- 

 tients continue the same, require circu- 

 lar motions. 



Newton, in investigating the geone- 

 trical pro[K)r(ion of the ellipse, dis- 

 covered that the spaces, inchuled be- 

 tween tlie radius vector, (or line drawn 



[April 1, 



from one of the foci to the periphery of 

 the ellipse) and a tangent to the cui-ve, 

 were equal in equal times; and hence 

 (hat the forces concerned in producing 

 these equal areas were represented by 

 the radius vector and the tangent. The 

 former he foimd to correspond with the 

 inverse duplicate ratio of its leng(hs, 

 and, therefore, ascribed their variation 

 to a supjKised attractive force in the 

 same ratio; and the latter, whicli cor- 

 res|Kinded with no force in nature, he 

 ascribed to an orignal impulse given 

 to them by the Deity at their creation. 

 This was highly poetical, and sub- 

 limely theological ; but it should be 

 considered that, although results of suc- 

 cessive natural powers may he repre- 

 sented for purposes of calculiition by 

 geometrical symbols, yet these sym- 

 bols cannot with any truth be consi- 

 dered as actual representations of pow- 

 eis iu nature. They are mathematical, 

 not physical data, and Newton argued, 

 in a circle, when he adopted the two 

 generic lines, a right line generated by 

 rectilinear motion, and a cuive line 

 which respects a centre, as symbols; and 

 then referred to the necessarily different 

 properties of a rigiit line and a curve, 

 as to operative powers of nature. 



Let us, however, drop these symbols, 

 and the false analogies drawTi from 

 (hem, and consider the subject with 

 the lights of reason and experience, 

 and with due respect to the constant 

 simplicity of nature, and the necessaiy 

 mechan ical secondary-causes wh ich pro- 

 duce natural phenomena. 



Whatever be the nature of the force 

 with which the sun acts on (he several 

 planets, it is evident that it is a com- 

 mon force to all ; and therefore at all 

 times equal in regard to each. 



If at any time it is unequal to a parti- 

 cular planet, as though the other planets 

 were on one side the sun, and jt were 

 then supposed that the sun's action were 

 at that time imequal in regard to that 

 one, and to the others ; yet an accidental 

 or occasional inequality from this cause 

 would not produce regular elliptic or- 

 bits, and regular pi'ogressions of the 

 line of Apsides. 



Again, it is fanciful to place the sun 

 in the foci of the ellipse of a particular 

 planet for the purpose of varying the 

 forces ; for in (his case, the line of Ap- 

 sides in all the planets ought to coin- 

 cide, which is not the case, and it is 

 ab.'iurd to require the sun (the common 

 force) to be in several foci at tlie same 

 (imf>. producing opposite results, 



III 



