130 HISTORY OF 



What has been hitherto rebted, is chiefly applicable to the 

 element of water alone ; but its fluidity is a property that it 

 possesses in common with several other substances, in other re- 

 spects greatly differing from it. That quality which gives rise 

 to the definition of the fluid, namely, that its parts are in a 

 continual intestine motion, seems extremely applicable to water. 

 What the shapes of those parts are, it would be vain to attempt 

 to discover. Ever}' trial only shows the futility of the attempt ; 

 all we find is, that they are extremely minute ; and that they 

 roll over each other with the greatest ease. Some, indeed, from 

 this property alone, have not hesitated to pronounce them 

 globular ; and we have, in all our hydrostatic books, pictures 

 of these little globes in a state of sliding and rolling over each 

 other. But all this is merely the work of imagination ; we 

 know that substances of any kind, reduced very small, assume 

 a fluid appearance, somewhat resembling that of water. Mr 

 Boyle, after finely powdering and sifting a little dry powder of 

 plaster of Paris, put it in a vessel over the fire, where it soon 

 began to boil like water, exhibiting all the motions and appear- 

 ances of a boiling liquor. Although but a powder, the parts of 

 which we know are very different from each other, and just as 

 accident has formed them, yet it heaved in great waves like 

 water. Upon agitation, a heavy body will sink to the bottoci, 

 and a light one emerge to the top. There is no reason, then, to 

 suppose the figure of the parts of water round, since we see 

 fheir fluidity very well imitated by a composition, the parts of 

 which are of various forms and sizes. The shape of the parts 

 of the water, therefore, we must be content to continue ignorant 

 of. All we know is, that earth, air, and fire, conduce to se- 

 jvirate the parts from each other. 



Earthy substances divide the parts from each other, and keep 

 tliem asunder. This division may be so great, that the water 

 will entirely lose its fluidity thereby. Mud, potter's clay, and 

 dried bricks, are but so many different combinations of earth 

 and water ; each substance in which the parts of water are most 

 separated from each other, appearing to be the most dry. In 

 some substances, indeed, where the parts of water are greatly 

 divided, as in porcelain, for instance, it is no easy matter to re- 

 o\'er and bring them together again ; but they continue in a man- 

 ner fixed and united to the manufactured clay. This circura- 



