THE LAWS OF FILMS. 



623 



ure of alcohol and water of exactly the specific gravity of oil. 

 Into the midst of this liquid he quietly introduced oil by means 

 of a funnel. The oil lay passive between the equal downward pull 

 of gravity and the upward lift of the alcohol and water. In this 

 way the forces which bound the oil particles together had free 

 play. The oil rounded itself at once into a sphere. For a time 

 there was, of course, some chemical action between the oil sphere 

 and the surrounding liquid ; but, in making his observations, 

 Plateau waited till these affairs had been settled between them, 

 and their relations became fixed. 



He then introduced into his oil sphere a rod, with a disk 

 smaller in circumference than the oil sphere about it. Both of 

 these were well oiled, and they entered the sphere without dis- 

 turbing it. The globe of oil hung in the water, with the rod 

 running through it in the posi- 

 tion of the earth's axis, and the 

 disk almost reaching to the line 

 corresponding with our equator 

 (Fig. 5). 



By means of a handle the rod 

 was turned, at first slowly, then 

 gradually and steadily faster. 

 The oil sphere slipped more easi- 

 ly around in its water socket 

 than it would around the re- 

 volving rod and disk, and there- 

 fore turned upon its own axis. 

 By varying his experiments, re- 

 volving his rod faster or slower, 

 Plateau made a miniature repre- 

 sentation of a world revolving 

 about its own axis ; he made his oil sphere throw off satellites, 

 which revolved about the central sphere ; he also, by what he calls 

 a trick, imitated Saturn with its attendant ring. 



He followed these experiments by using outlined frames of 

 wire, such as we used for our soap films. These he adjusted 

 around his hanging sphere of oil, and with a syringe withdrew 

 the oil, making first a cube of oil with unsupported faces; and 

 finally, as more and more oil was withdrawn, there resulted a 

 system of oil films, each face of which was in contact with the 

 water, exactly like those in Figs. 1 and 2. 



This was the manner in which such systems of films were first 

 reached ; and, historically, the experiments have an interest in 

 their relation to the subject of films as well as for the proof they 

 offer that the material of which the films are formed has nothing 

 to do with the forms they take on. Plateau went on from his oil 



Fig. 5. 



