ia^S Obfervafions on the Property of Oil, &c. 



againft the water, and an attradlive power among themfelveg, 

 they would be prevented from fpreading, in an uniform man- 

 ner, over the furface of the water : they would rather form 

 infalated globules ; and, as they touch the water, would 

 equally recede, and proceed towards the bank or any other 

 folid body. Oil, therefore, ag it is lighter than water, mull 

 float on its furface when poured upon it, and, according to 

 the laws of hydroftatics, endeavour to extend itfelf in a la- 

 teral direftion ; and on account of the ftrong adhefion of its 

 particles, muft form an extraordinary fine and continued 

 ftratum on the furface of the water. This difFufion, how- 

 ever, fuppofes that the furface cf the water is horizontal ; 

 it therefore feems to follow, that the whole power of the oil 

 confifts in preventing the formation of new waves in the 

 places on which it has been poured ; but that it cannot be 

 in a condition to difperfe thofe which have been already 

 formed. The billowy agitation of water fuppofes that fome 

 part of its furface has been previouflv raifed. Bodies which 

 float upon it oppofe this rifing by their gravity, confequently 

 the billowy movement, and in part dcfiroy it. 



It appears therefore, to fome philofophers, that this cele- 

 brated property of oil does not confifl; fo much in its fluidity 

 and toughnefs, as in its being a lighter body than water. 

 From this it vi-ould follow, that all bodies lighter than water, 

 and at the fame time more diftended, fuch as drops or malTes 

 formed by oil, mull produce the fame effett, but in a higher 

 degree. Achard recommends for this purpofe clofe leathern 

 vefTels, through which the water cannot penetrate ; or, what* 

 would be flill better, tin-plate boxes of from fix to eight feet 

 content in the bafe and two feet in height, which mufl be 

 filled with air, but rendered impenetrable to water. Ships, 

 he thinks, without much increafing their lading, might al- 

 ways carry with them fome dozens of thefe velTels or boxes, 

 to be thrown overboard, faftened to the fliip with ropes, in 

 pafe the agitation of the water fnould thfeaten danger. Achard 

 niade experiments, on a fmall fcale, with tin-plate boxes of 

 6 this 



