of a Liquid Mass without Weight. 357 



tion of its surface. For instance, we know that films formed 

 upon rings or frames made of iron wire that has not been oxi- 

 dized break immediately, or last only for a very short time; and 

 according to the Abbe Florimond, soap-bubbles of a much larger 

 size can be blown with a glass pipe than with a clay one &c. 



From this examination of all the accessory circumstances, it 

 follows that a film of given size will last longest if it is a plane 

 horizontal film, attached all round to the side of a glass vessel, 

 entirely shielded from evaporation, and protected from the mo- 

 tion of the surrounding air, and, as much as possible, from the 

 tremors conducted along the ground. Now all these conditions 

 were fulfilled in the case of a film 7 centims. in diameter men- 

 tioned in my Seventh Series, formed of the glycerine solution 

 and placed inside a bottle : accordingly this film lasted eighteen 

 days. 



I next pass to another subject. The beauty of the film-figures 

 of the glycerine-solution naturally gives rise to the wish to have 

 them entirely permanent. In the case of one of them (the 

 sphere) this object is attained, as every one knows, by means of 

 molten 'glass ; but the production of other figures in this mate- 

 rial, especially of such as are formed by an assemblage of films, 

 would present difficulties, and in any case it would not be con- 

 venient. The first idea that suggests itself is to employ a liquid 

 which produces films that become solid by simple evaporation in 

 the cold, such as collodion, solution of albumen, &c. ; but with 

 a liquid of this kind no result can be obtained except by limiting 

 our attempts to figures of very small size. 



Hence, in order to succeed in producing figures of tolerable 

 size, we are obliged to have recourse to substances which, like 

 glass, are liquid only at high temperatures, and to seek for one 

 which fulfils the double condition of not requiring a very high 



i temperature to melt it, and of being capable of extension, in the 

 molten state, into films of sufficient size. I succeeded almost 

 completely with a mixture of one part of pure gutta percha and 

 five parts of resin, kept at a temperature of about 150° C. ; the 

 frame employed was a cube measuring 5 centims. along the edge. 

 The system of films that was produced was very firm, and lasted, 

 I think, more than two years, when a slight blow reduced it to 

 fragments — from which we must conclude that the constitution 

 of the films had undergone a gradual change. I think one 

 would succeed still better, and that the gradual alteration would 

 be less, if a somewhat larger proportion of resin were employed. 

 I conclude the part of my work which is specially devoted to 

 liquid films by a succinct account of every thing that, as far as 

 my knowledge goes, has been published in relation to such films 





