632 PHILOSOPHICAL TRANSACTIONS. [aNNO 1723. 



pustules to Others, which produced the same effects. Two large villages near 

 the harbour of Mil ford, are more famous for this custom than any other, viz. 

 St. Ishmael's and Marloes. The old inhabitants of these villages say, that it 

 has been a common practice with them time out of mind; and, what was more 

 remarkable, one William Allen, of St. Ishmael's, QO years of age, who died, 

 about 6 months since, declared to some persons of good sense and integrity, 

 that this practice was used all his time; that he very well remembered his 

 mother's telling him, that it was a common practice all her time, and that she 

 got the small pox that way. 



These, together with the many other informations, I have met with from 

 almost all parts of the county, confirm me in the belief of its being a very 

 antient and frequent practice, among the common people; and to prove that 

 this method is still continued among us, one Joan Jones, a midwife, 70 years 

 of age, solemnly declares, that about 54 years since, having then the small 

 pox, one Margaret Brown, about 12 or 13 years of age, bought the small pox 

 of her ; that the said Margaret Brown was seized with the small pox a few 

 days afterwards ; that the said Margaret Brown had not had the small pox a 

 2d time. She further says, that she has known this way of procuring the 

 small pox practised from time to time, above 50 years; that it has been lately 

 used in her neighbourhood, and that she knows of only one dying of the said 

 distemper, when communicated after the method aforesaid, which accident iiap- 

 pened within these 2 years last past ; the person who miscarried, a. young 

 woman about 20 years of age, having procured the distemper from a man then 

 dying of a very malignant small pox. Further, that hundreds in this country 

 have had the small pox this way, is certain ; and it cannot produce one single 

 instance of their ever having them a second time. 



Haverford Westy Feb. 15, 1723. 



Experiments^ to prove that the Force of moving Bodies, is proportionable to 

 their Velocities : or rather that the Momentum of moving Bodies is to be 

 found by multiplying the Masses into the Velocities. By the Rev. John 

 Theophilus Desaguliers, LL.D. F.R.S. N°375, p. 269. 



M. Leibnitz, I believe, was the first that opposed the received opinion, con- 

 cerning the quantity of the force of moving bodies ; by saying, that it was to 

 be estimated by multiplying the mass of the bodies, not by their velocity, but 

 by the square of it. But, instead of showing any paralogism, in the mathe- 

 matical demonstrations, made use of to prove the proposition, or any mistakes 

 in the reasonings from the experiments made to confirm it, he uses other me- 

 diums to prove his assertions; (Acta Erudit. ad ann. 1686, p. l62;) and with- 



