ON THE MOTION OF WAVES. 361 



The same causes which raise water into waves, must evidently 

 produce the like eftect on other fluids, but in different degrees, ac- 

 cording as the fluid is more or less heavy, as its particles adhere 

 more or less forcibly to each other, and probably likewise according 

 as there is a greater or less degree of attraction between the fluid 

 and the other body, which gives it the impulse. 



When a stone or other heavy body is dropped on the surface of 

 oil, the waves are not nearly so high, nor so quick, neither do they 

 spread so far as the waves of water. This eftect is evidently owing 

 to the clamminess, or great degree of adhesion between the particles 

 of the oil. 



If the waves upon oil be attempted to be raised by the force of 

 wind, it will be found very difficult to succeed even in a moderate 

 degree. This difficulty is, in a great measure, owing to the attrac- 

 tion between the particles of oil ; but besides this, there may be 

 less attraction between oil and air, than between the latter and 

 water; for water always contains a certain quantity of air; and if 

 it be deprived of that air by means of boiling or otherwise, a short 

 exposure to the atmosphere will enable the water to reimbibe it. 



It is likewise probable, that the surface of wafer, even when 

 stagnant, may not be so smooth as the surface of oil ; so that the 

 wind may more easily catch into the inequalities of the former than 

 of the latter. 



It is remarkable that the effect of the wind upon water may, iu a 

 great measure, be prevented or moderated, by spreading a thin 

 film of oil on the surface of the water. 



No great quantity of oil is required for this purpose; for, though 

 oil be very clammy and adhesive to almost all other bodies ; yet 

 when dropped upon water, it will instantly spread and extend itself 

 over a vast surface of water; and it will even drive small floating 

 bodies out of its way, acquiring, as it seems, a repulsive property 

 amongst its own particles. 



This repulsion may be shewn in the following amusing manner : 

 Cut a light shaving of wood, or of paper, in the form of a comma, 

 smear it with oil, then place it upon the surface of a pretty large 

 piece of smooth water ; and the bit of wood or paper will be seen 

 to turn round in a direction contrary to that of the point, which is 

 occasioned by the stream of oily particles issuing from the point, and 



