M PHILOSOPHICAL TRANSACTIONS. [aNNO 1785, 



perature of 32 degrees for a quarter of an hour ; the little bit of ice continued 

 nearly the same. I now weighed it, after carefully wiping the glass, and found 

 it heavier than the water was at first 1 division of the beam. Lastly, I took out 

 the weights, and found the beam exactly balanced as before the experiment. 



The acquisition of weight found by water being converted into ice, may arise 

 from an increase of the attraction of gravitation of the matter of the water ; or 

 from some substance imbibed through the glass, which is necessary to render the 

 water solid. Which of these positions is true, may be determined by forming a 

 pendulum of water, and another of ice, of the same length, and in every other 

 respect similar, and making them swing equal arcs. If they mark equal times, 

 then certainly there is some matter added to the water. If the pendulum of ice 

 is quicker in its vibrations, then the attraction of gravitation is increased. For 

 there is no position more certain, than that a single particle of inanimate matter 

 is perfectly incapable of putting itself in motion, or bringing itself to rest ; and 

 therefore, that a certain force applied to any mass of matter, so as to give it a 

 certain velocity, will give half the quantity of matter double the velocity, and 

 twice the quantity, half the velocity ; and, generally, a velocity exactly in the 

 inverse proportion to the quantity of matter. Now if there be the same quantity 

 of matter in water as there is in ice, and if the force of gravity in water be -s-tt-s-t 

 part less than in ice, and the pendulum of ice swing seconds,, the pendulum of 

 water will lose ^-g-^-o of a second in each vibration, or 1 second in 'ZSOOO, which 

 is almost 3 seconds a day, a quantity easily measured. 



I shall just take notice of an opinion which has been adopted by some, that 

 there is matter absolutely light, or which repels instead of attracting other matter, 

 I confess this appears absurd to me ; but the following experiment would prove or 

 disprove it. Supposing, for instance, that heat was a body, and absolutely light, 

 and that ice gained weight by losing heat ; then a pendulum of ice would swing 

 through the same arc in -rr-ro-ff ^^ss time than a similar pendulum of water ; for 

 the same power would not only act on a less quantity of matter, but a counter- 

 acting force would also be taken away. I shall only observe, that heat certainly 

 diminishes the attractions of cohesion, chemistry, magnetism, and electricity ; and 

 if it should also turn out, that it diminishes the attraction of gravitation, I should 

 not hesitate to consider heat as th6 quality of diminution of attraction, which 

 would in that case account for all its effects. ' 



We come, in the next place, to take notice of the 2d part of the experiment, 

 viz. that the ice gained an 8th part of a grain on being cooled to 12 degrees of 

 Fahrenheit's thermometer. In this case, a variation may arise from the contrac- 

 tion of the glass vessel, and consequent increase of specific gravity in proportion 

 to the air. But it is unnecessary to observe, that this would be so very small a 

 quantity as not to be observable on a beam adjusted only to the degree of sensi- 



