VOL. XXX.] PHILOSOPHICAL TRANSACTIONS. 321 



cheek and lower jaw were cut away, it is grown up again, and is of the ordi- 

 nary colour of the skin, and like the other side of the face; so that the hair 

 grows on that side of the face as well as on the other, which he usually shaves ; 

 which is as surprising as any thing in the whole affair. 



An Account of an Experiment to prove an interspersed Facuum ; or, to show 



that all Places are not equally Jul I . By J, T, Desaguliersy M. A, F.R.S. 



N° 354, p. 717. 



On dropping a guinea and a piece of fine paper; then a guinea and a feather 

 together, from the top of an exhausted glass- receiver, about 20 inches high; 

 they both fell to the bottom at the same instant of time. Now since the chief 

 resistance of a medium (and indeed almost all of it) depends on the quantity 

 of its matter (see Newton's Princ. 1. 2, p. 40) ; therefore this diminution of 

 resistance, by which the feather fell as soon as the guinea, showed a diminution 

 of the quantity of matter, and consequently proved an interspersed vacuum. 



Some plenists in England objecting against the shortness of the glass- 

 receiver ; as if the difference of time in the fall of the two bodies, which 

 they affirmed to be real, could not be perceived in such a glass; and some 

 philosophers from abroad affirming that in a glass-receiver 7 or 8 feet long, 

 there would be such a manifest difference in the time of the fall of the said 

 bodies, as to show this experiment no proof of a vacuum ; though at the same 

 time, some of the objectors well knew that there could be no receivers of 

 half that length made at the glass house, and therefore thought the experiment 

 impracticable. To obviate this, I contrived a machine for the purpose, which 

 consisted of a strong wooden frame, 15 feet high, that held the air-pump and 

 4 cylindric glass-receivers of about 2 feet long each, and d inches diameter: 

 having set the first of these upon the air-pump plate, I laid on the top of it a 

 brass-plate of 7 inches diameter, with an oiled leather fixed to it above and 

 below, and a hole through the middle, between 4 and 5 inches diameter; then 

 on that plate I set the next receiver, with a like plate at top ; and after the 

 same manner fixed the other two with plates between them : the upper receiver 

 being a little narrower at the neck, went into the hole of a board, by which it 

 was screwed down pretty hard on the other glasses, and fixed to the whole 

 machine. On the top of this upper receiver I laid the brass plate, wet leather, 

 and brass springs, which contained the bodies to be dropped. 



When the receiver was full of common air before pumping, the guinea came 

 to the bottom, just as the paper was about the middle of the second glass; but 

 when the receiver was exhausted, the guinea and paper came to the bottom 

 precisely at the same instant of time. , , * 



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