On the Contraction of IVater ly Heat. \bh 



have at different periods been offered to discredit, and to 

 bring it into doubt. 



The first observation relative 4o this subject was made by 

 Dr. Croune, towards the close of the 1 7th century, while 

 engaged in investigating the phaenoniena of the great and 

 forcible, though familiar, expansion which happens to water 

 at the instant of freezing; a matter winch occupied, in a 

 considerable degree, the attention of his fellow-members 

 of the Royal Society of London in the earlier years of that 

 institution. 



I shall relate, in his own words, his first observation : — 

 " I filled a strong bolt-head about half way up the stent 

 with water, a day or two before the great frost went oif, 

 marking the place where the water stood ; and placing it 

 in the snow on my leads, while I went to put some salt to 

 the snow, I found it above the mark so soon, that I thonght 

 the mark had slipt down, which I presently raised to the 

 water, and as soon as ever I mixed the salt with the snow, 

 the water rose very fast, about one-half inch above it. I 

 took up then the glass, and found tlic water all fluid still : 

 it was again set down in the salt and snow ; but when I 

 came, about an hour after, to view it, the ball was broken, 

 and the water turned to hard ice, both in the ball and 

 stem*." 



From this experiment Dr. Croune drew the conclusion, 

 that water, when subjected to cold, actually began to ex- 

 pand before it began to freeze. On annoimcing it, how- 

 ever, to the Royal Society, on the 6th of February lf)S3, 

 Dr. Hooke immediately expressed strong doubts, and as- 

 cribed the ascent of the water in the neck of the vessel to 

 the shrinking of the glass occasioned by the cold. 



To obviate this objection, and to preclude, as far as was 

 possible, the influence of the change of capacity in the ap- 

 paratus from an alteration of its temperature, a bolt-head 

 was immersed in a mixture of salt and snow, and into it, 

 when cooled, was poured, to a certain height, water pre- 

 viously brought to nwr the freezing point. The water be- 

 gan instantly to rise as before, and \\ hen it had ascended 

 about one-fourth of an inch in the stem, the vessel was 

 taken out, the whole water remaining fluid. 



These experimcnl-', supported by others of a similar na- 

 ture, communicated by Dr. Slare to the society on the L'Olh 

 of the same month, appear to have satisfied its members, 

 in general, of this fact, tiiat water, whtn on the point of 



• Bir«,2k'« History c 1' the Royal "uciefy, vol. !v p. C'J;?. 



congealing, 



