ft3^ Ohfervatmis on the Proferty of Oil 



fpeedily over a large fpace of water, fo that it formed a thin 

 covering to it, vyhich reflefted prifmatic colours, lie rcfolved 

 to make fome farther experiments ; and though they did not 

 all fucceed ficcording to his wifh, he declared himfelf con-» 

 vinced of the truth of the phenomenon. 



One of thefe experiments I muft here mention; for, though 

 it does not appear very favourable to his ideas refpefting the 

 efficacy of oil in calming the waves, it at any rate (hews that 

 oil has a great influence on the motion of water. He difco- 

 vered that oil excites on th? water a kind of waves, under 

 circumftances when neither water alone nor oil could pro- 

 duce the like. He fufpended a glafs half filled with water, 

 and having inade it to fwing backwards and forwards, after 

 the manner of a pendulum, the water remained at perfect 

 reft. The cafe was the Auiie when the glafs was half filled 

 with oil ; but as foon as lie had poured oil upon the water, 

 and c(?ntinucd the fwinging of the glafs, the furface of the 

 yibvqit.ng oil remained fnicoth and even, while the water 

 below it was thrown into a regular agitation like that of the 

 billows of the fea, 



Franklin conllders tliis phenomenon, which I have con- 

 firmed by experiments, to have in it f(;mcthing fingular, and 

 difficult to be explained. The caufe of it, however, may 

 perhaps lie in the dilTercnce of the fpecific gravities of thefe 

 twp fluids, by which they are fufceptible of the impulfe to 

 movement in different degrees; and by the effort which the 

 oil makes, on account of its lightnefs, to occupy the upper 

 place on the furface, the watpr is violently agitated. 



When a drop of oil is poured upon water in a ftate of reft, 

 35 % example in a bafjn, a fine vapour immediately arifes 

 and covers the furnace of the water. It emits coloured rays, 

 And difperfi.-.-, fn.all bits of paper thrown upon the fpreading 

 drops. When the fpace on which the drop falls is fmall, it 

 dnes not fprpad itfelf; but feems, as it were, to be attradled 

 iowards its ccnlre. When a bit of paper, twifted togethe;- 



