154 On the Contraction of IVater lij Heat. 



40th or 41st degree. Between this point and the 4'_'d or 

 4:kl, it siiilVrs s^carcely any perceptible change ; but when 

 heated bevund the last-mentioned decree it begins to ex- 

 pand, and increases in volunic with every subsequent rise 

 t.)l' temperature. 



Daring the abstraction of caloric, the peculiarity in the 

 ronslitution of water equally appears. Warm water, as it 

 cools, shrinks, as other bodies do, till it arrives at the tem- 

 perature of 43" or 49". It then suffers a loss of two degrees 

 vvitiiout any alteration of density. But when further cooled, 

 it begins to dilate, and continues to dilate, as the tempera- 

 ture falls, till congelation actually commences, whether this 

 ■ovcurs as soon as the water reaches the 32d degree, or after 

 U has descended any number of degrees below it. 



Supposing this peculiarity of water to be established, it 

 must appear, indeed, a very odd circumstance, that heat 

 should produce contraction in this fluid, while it causes 

 expansion in other bodies ; and no less strange, that within 

 one ra^ige of temperature it shotiJd contract, and in another 

 t'xpand, the very same substance. Before a deviation from 

 s« general a law should be received as matter of fact, the 

 proofs of its existence ought to be clear and indisputable. 



The experiments hitherto published, from which this sin- 

 gularity has been deduced, have all of them been performed 

 upon water contained in instruments shaped like a thermo- 

 mcf»r glass, and consisting of a ball with a slender stem ; 

 and the expansive or contractive effects of heat and cold have 

 been inlcrred from the ascent or descent of the fluid in the 

 stem. 



To such experiments it has been objected, that the di- 

 Tnensions and capacity of the instrument undergo so much 

 change, from variation of temperature, that it is difficult, 

 if not impossible, to determine how much of the apparent 

 anomaly ought to be imputed to such changes, and that it 

 is not improbable that the whole of it may be ascribed to 

 them. 



The object of this paper, which I have now the honour to 

 read to -the society, is to prove, by a set of experiments, 

 conducted in a manner altogether different, that the com- 

 mon opinion is founded in truth, and that water presents 

 itself as that strange and unaccountable anomaly which I 

 have already described. 



it is worth while, before detailing my experiments, to 

 give a short account of those observations which led to the 

 discovery of the fact, and which in succession have extended 

 cur knowlcdiie of it, as well as of those observations which 



ha\e 



