WAVES BETWEEN ©IL AND WATER. 



my paper iu your following number for October 181(7, 

 which I shall also recall for the same motive in a following 

 communication, and I hope that the whole together will 

 induce Dr. May cock to change his system. 



I am, with great regard, sir, 



Your most obedient servant, 

 Windsor, J. A. DE LUC. 



July the 10th, 1812. 



VIII. 



Explanation of a hydrostatical Phenomenon observed by 

 Franklin: by Robinet*. 



Agitation of 

 water under- 

 neath oil. 



The pheno- 

 menon capa- 

 ble of varia- 

 tion. 



The facts ic- 

 sult from two 

 known princi- 

 ples. 



Tendency of i 

 fluid to a level. 



JLF you put water and oil into a tumbler, suspend the tum- 

 bler by a string, and give it a gentle swing, you will perceive 

 nothing particular at the surface of the oil ; but the surface 

 of the water beneath will appear agitated, and form considera- 

 ble waves. Such was the phenomenon observed by Franklin, 

 and with which he was puzzled no doubt merely because he 

 had not time to examine it: for that great man had so acute 

 an eye in observing nature, that he scarcely ever failed to 

 seize those connexions of facts, that constitute properly what 

 we call physical laws. His confession of his ignorance on 

 this occasion merely proves, that his modesty knew how to 

 avail itself of his being too much occupied to examine every 

 thing. 



This phenomenon is capable of assuming very different 

 forms, by varying the circumstances by which it is produced. 

 I shall confine myself here to that observed by Franklin, 

 because it is one of the most complicated. 



The facts that compose this phenomenon, some of which 

 are known to all the world, are the result of two hydrostati- 

 cal principles, well known separately, but not yet considered 

 together; that by which liquids seek their level, and that 

 with the discovery of which Archimedes was so delighted. 



By the first, all the parts of a liquid equally heavy, and 

 perfectly movable on each other, tend toward the centre of 



* Abridged from the Journ. de Phys , vol. LXV, p. 277. 



the 



