3<}0 CONTRACTION OF WATER BY HEAT, 



it is bable Now, if this polarity operates with fo much energy as t£ 



that the arrange- impart almoft irrefiftible expanfive force at temperature 3'2°, 

 ment and the j t ; s re afonable to fuppofe that it may begin to exert its in- 



expanlion may . . ' . . jo 



begin before fluence, lliough in a far inferior degree, at temperatures lome- 

 foJidity enfues, w } ia t more elevated. The expanfion, therefore, that takes 

 place, during the fall of temperature from 40°, may be im- 

 puted to the particles beginning or affecting to aiTume that 

 new arrangement which their polarity afligns them, in which 

 arrangement thefe particles occupy more fpace than before. 

 and the con- Again, when heat caufes water of 32° to contract, upon 



trar y» the fame principle, it may be conceived to operate, by coun- 



teracting the fmall portion of the difpofition to polarity that 

 furvives the liquefa&ion. 



I am afiaid that we cannot reft fatistied with this explana* 

 tion. We mud not be deceived by the plaufibility of it. 



The ftate of perfect fluidity depends upon the circumitanci', 

 /that the particles o( any body admit of ready motion upon 

 each other, and that the change of relative fituation meets 

 with little or no fenfible refiftance. 

 Objection. This Water certainly poflefles fluidity in a great degree, and its 

 advance towards p ar tj c les muft of courfe encounter but little refinance, as they 

 ought to Impair glide the one upon the other. But if thefe particles dial! 

 the fluidity ; begin to exert any degree of polarity, by which certain faces 

 become -more difpofed to attach to each other than certain 

 others, this tendency would neceflarily oppofe that indifference 

 with regard to pofition, which is eiTential to fluidity, and of 

 courfe muft impair the fluidity, and induce fome degree of 

 tenacity or vifcidity. 

 which does not To appearance, however, water at 32° has its fluidity as per- 

 appear to be the f e ^ as at temperatures confiderably elevated. Unwilling to 

 trull to appearance, where experiment might decide, I have 

 attempted in various ways to afcertain whether the water 

 fuffers any fenfible diminution in this refpeel while it is 

 expanded by cold. The following method I deem the moft 

 correct, 

 Experiment! For the purpofe, I employed a gravimeter, the one contriv- 



with Nichols's ec j ^ j^ r# Nicholfon for discovering the weight and fpecific 

 gravime e . gravity of folids. 



This is a convenient inftrument, but, unfortunately, it is by 

 no means fo ticklifh as a balance. Duly loaded, fo as to be 

 equiponderant with the water in which it is plunged, Mr. 



Nichollbn 



