Intelligence and Miscellaneous Articles* 69 



addressing to the Academy a summary of the propositions with 

 the aid of which I believed I could explain, at the August meeting 

 of the Royal Academy of Belgium, how a small quantity of oil 

 spread out upon a large surface can overcome an enormous quan- 

 tity of vis viva of the waters*. 



1. The quantity of work necessary for increasing by 1 square 

 metre the free surface of a mass of water is about 0*0075 kilo- 

 gramme-metre ; this work is stored up, in the form of potential 

 energy, in the fresh surface layer of the water ; the thickness of the 

 layer in which that energy resides does not reach -g-^-J^o millim. 



2. Reciprocally, if the free surface of the water rapidly dimi- 

 nishes, to each square metre of surface lost an energy of motion 

 equivalent to 0*0075 kilogramme-metre corresponds. 



3. Let us in thought isolate a mass of water having a base of 

 1 square metre and a thickness of 1 metre, and imagine that a 

 mechanical action, such as the wind, rapidly rolls up a superficial 

 layer of 1 square metre base and -^iwu millim. thickness, laying 

 bare a fresh layer of the same extent ; then the potential energy of 

 the first layer will be entirely transformed into energy of motion. 

 If all the layers in succession, each -g-o-J^-g millim. in thickness, are 

 likewise rolled up, the application of the principle of vires vivce 

 shows that theoretically the cubic metre of water can store up 

 150,000 kilogramme-metres of work, capable of impressing on the 

 total mass a velocity of 54*2 metres. 



4. If a superficial layer of water of 1 square metre surface is 

 caused by the action of the wind to slide over the next layer, of the 

 same extent, the latter, being covered by the former, loses its po- 

 tential energy, but acquires an equivalent quantity of energy of 

 motion • if the action of the wind makes a fresh layer slide over 

 the first two, there is again developed a vis viva equivalent to the 

 lost potential energy of the free surface, and so on. 



5. Let us now suppose that a layer of pure water slides over a 

 layer next to it, covered with oil ; from that time the potential 

 energy (0*0055 kilog.-m.) of the water covered by a thin greasy 

 layer is replaced by the potential energy of the free surface of 

 pure water (0'0075 kilog.-m.), an energy augmented by those of the 

 two surfaces of contact of the submerged thin layer of oil with 

 the water below and the water above : the value of each of these 

 latter is, according to M. Quincke's measurements, 0*002 kilog.-m. 

 Therefore the sliding of the layer of pure water over the oily layer 

 has produced a gain of potential energy of 0*006 kilog.-m. per 

 square metre. But to such a development of potential energy 



* It is highly desirable that trials should be made at the mouth of 

 the Seine for the purpose of ascertaining if a relatively minute quantity 

 of oil can, as the facts already known and my theory of the potential 

 energy of liquid surfaces would lead us to presume, prevent the disastrous 

 effects of the violent eddy of the tide. In case of success the employment 

 of oil during storms in harbours, in the vicinity of lighthouses, at dan- 

 gerous parts of the coasts, &c. would become a duty. 



