[ 54 ] 



XI. Olservations oti the Expansion and Contraction of 

 Water. By William Ckane, F.R.M.S. Edin. 



JQ/VERv deviation from the general cifccts of caloric forms 

 an important subject for investigation, and claims ihe at- 

 tention both of ihesludenl and the philosopher. Amongst 

 these curious and interesting facts, that water at the tempera- 

 ture of 40" has its maximum density, and on being reduced 

 to a lower, degree begins to expand ui-.til it is convened 

 into ice, has given rise to many hvpothcses and theories 

 respecting its cause. Some have supposed this to be owing 

 to the conlraction of the vessel in which the water is con- 

 tained. ■ One of the most strenuous supporters of this 

 opinion is Mr. Dalten, who says, *' it is only apparent;" 

 although the experiments both of Dr. Hope and Count 

 Kumford were made with the greatest care and precision, 

 as were also those of Lefevrc Gincau. 'J he result of Mr. 

 Dalton's experiments, when a glass vessel is employed, is 

 certainly very much in favour of what he maintains, as, ac- 

 cording to the tables in Dr. Thomson's Chemistry, the con- 

 traction of the glass and the expansion of the water coin- 

 cide; vet this is not the result of the experiments made 

 upon water contained in different vessels, as in brown 

 earthen ware, queen's ware, iron, copper, &c. The coinci- • 

 denee, therefore, as the doctor observes, is (miy apparent; 

 for the other bodies deviate as their expansion increases. 

 Mr. Leslie, in his Inquiries upon the Nature, &c. of Heat, 

 seems to be nearly of the same opinion. Others have adopted 

 the idea of its arising from a peculiar arrangement of its 

 particles which observe a certain polarity, as is shown by 

 the position of its crystals; and this was the opinion ol the 

 illustrious Dr. Black. 



As water is a body the particles of which possess great 

 mobility among themselves, and tlie shape of a body that 

 moves with the greatest ease being; a sphere ; let us consi- 

 der tha* this is the form of a panicle of water when at the 

 ^C and above, or, according to JNIr. Dalton*, at the 36", 

 which he estimates to be its maximum density. In the 

 following part of this paper I prefer the 40'', as between that 

 and ag'' is the point agreed to by (he majority of writers, 

 and which agrees wiih the experiments 1 have made. The 

 difficulty of proving this to be the shnpe of an atom of wa- 

 ter is perhaps in some measure rtmoved by considerin"" 

 the figure which a globule of \\ater assumes when thrown 



* Dr. Henry "s ElenicnU of Chemistry. 



UpOil 



