1SI3.] Meynoirs of the Manchester Society. 465 



plied into the velocity, or into the square of the velocity. The 

 last of these opinions was adopted hy Hooke and by Huygens in 

 consequence of their observations on the motions of pendulums. 

 It was also adopted by Smeaton in consequence of his experi- 

 ments on the mechanical action of ^vater. It was embraced by 

 Leibnitz, and by his particular friends and supporters, the Ber- 

 noullis. And as the opposite opinion had been advanced by 

 Newton, it became involved in the Leibnitzian controversy with 

 the Newtonians. All the followers of Leibnitz embraced his 

 determination, while the Newtonians as strenuously adopted the 

 opinion of Newton. The French were induced to coincide with 

 the Nevi^tonians, because the same measure of force had been 

 employed .by Descartes. Thus the measure of force adopted 

 came to be the distinguishing feature of two opposite and hostile 

 sects, and each party rather struggled for victory than for the 

 cause of truth. That this party spirit is not quite extinguished 

 in tbis country I had a very remarkable proof soon after the 

 publication of Dr. Wollaston's lecture on the subject in 1806. 

 1 was told by a very sensible Gentleman, a good mathematician, 

 and one who had attended particularly to natural philosophy, that 

 Dr. Wollaston must be ignorant of the first principles of me- 

 chanics, because he defended the opinions of Mr. Smeaton. 

 Such is the zeal that still remains in this country in favour of the 

 Newtonian doctrine. Mr. Ewart supports the opinion of Smeaton 

 with great force of reasoning. The essay is remarkable for the 

 extensive knowledge of the subject which the author displays, 

 and for the great perspicuity of his reasoning, which is the con- 

 sequence of this extensive knowledge. He gives a number of 

 examples, which he considers as inconsistent with the common 

 notion, discusses these examples, and gives us a very full history 

 of the opinions of mechanical writers on the subject. I must 

 acknowledge that some of his cases appear to me fully capable 

 of solution according to the common notion; while others are 

 so complicated that it is difficult to disentangle them. The most 

 striking cases in favour of the Leibnitzian doctrine are those in 

 which, if we adopt the common opinion, a rotatory motion 

 seems to be produced without any force at all. We recommend 

 Mr. Ewart's essay to the attention of mechanical philosophers, 

 as by far the best defence of the Leibnitzian doctrine that we 

 have ever seen, and as a striking proof of the sagacity and ex- 

 tensive knowledge of the author. 



6, Accoimt of a remarkable .Effect produced ly a Stroke of 

 Lightning ; in a Letter addressed to Thomas Henry, Esq. F.R.S. 

 &c. President of the Literary and Philosophical Society, from 

 Matthew Nicholson, Esq. IVith remarks on the same by Mr. 

 Henry.] This contains an account of a very uncommon acci- 

 dent, which happened at Mr, Chadwicke's house, about five 



