VOL. XXXVIII.j PHILOSOPHICAL TRANSACTIONS. 6 1 () 



of mathematics and astronomy at Utrecht, communicated to him the following 

 experiment, made in opposition to that above, by Mr. Professor Gravesande. 

 In this last, a spring equally bent every way, pushes forward unequal quantities 

 of matter successively, and in every experiment the product of the mass of the 

 body by the square of the velocity is the same; and therefore, as the quantity 

 of motion must always be the same from the same cause, viz. the same tension 

 of the spring, it follows, by every experiment, that it is as the mass multiplied 

 into the square of the velocity. ■ 



Exper. 1. — The pendulous cylinder is shot by the spring, from 0° to 7°, 

 measured on a tangent line. 



Exper. 2. — The cylinder with a leaden weight in it, that makes its weight 

 double, is shot forward to 4^^°. 



Exper. 3. — The cylinder with a weight in it that made its weight triple, was 

 shot forward to 4'^, and a little farther. 



Exper. 4. — The cylinder with a triple weight of lead, so as to quadruple the 

 whole weight, was shot forward to 3^°. 



These 4 experiments at first seem agreeable to the new hypothesis; for ac- 

 cording to the old, the cylinder in the 2d experiment ought to have gone but 

 to 3i°, in the 3d experiment but to 34^°; and in the last but to 2". 



But if we take in the consideration of time, all will be reduced to the old 

 principle. As for example, let us compare the first and last experiments. In 

 the first, the spring during a certain time acts on the cylinder, which is driven 

 forward with the velocity 8. When the quadrupled weight is driven forward 

 with the velocity 4 instead of 2, it is because the same spring acts twice as long 

 on the cylinder before it ceases to impel it; and certainly the same cause acting 

 twice as long must produce a double efl^ect. 



On Quicksilver. By Herman Boerhaave,* Phil, et M. D. Professor of Physic 

 at Leyden, &c. N° 430, p. 145. An Abstract from the Latin. 



In this paper Professor Boerhaave gives an account of a numerous set of ex- 

 periments nmde upon quicksilver, with a degree of labour and perseverance 

 rarely equalled.-}- From these experiments he showed, that pure quicksilver is 

 convertible into a black powder, possessing considerable acrimony, by long 

 continued agitation or concussion in a glass-bottle; that from this powder liquid 

 quicksilver is again obtainable by distillation in a strong heat; that quicksilver 

 is convertible into a similar black powder by exposure for some months to a 



* Of this celebrated professor an account has been given at p. 556', vol. v, of these Abridgments, 

 t In these experiments Dr. B. distilled a given quantity of quicksilver above 500 limes. 

 4 K 2 



