270 Mr. S. P. Thompson on Permanent Plateau's Films. 



porate, leaving films of greater or less tenacity. He was 

 unsuccessful with collodion and with albumen. A solution of 

 gutta-percha in bisulphide of carbon gave better results. The 

 system of films upon a cubical frame of 2 centims. side was 

 preserved for several months, but eventually fell to powder. 

 The same substance refused to form a film upon a frame of 3 

 centims. side. Glass, which in the single instance of the 

 spherical film or bulb is so familiar, presents too many diffi- 

 culties to be applicable for the production of the film-figures. 



Schwartz* succeeded with much ingenuity in obtaining the 

 anticlastic film-surface upon a skew quadrilateral frame whose 

 sides were 3*5 centims. long, with gelatine. 



Prof. Machf imitated the system of films developed upon a 

 tetrahedral frame with thin laminae of caoutchouc covering 

 the sides, and drawn together when the air was exhausted 

 from within. 



Better results have been yielded by viscous liquids which 

 solidify at temperatures moderately low. 



M. Pottier, of Ghent, has obtained films of considerable 

 dimensions with a mixture, suggested by Bottger in 1838 for 

 blowing bubbles, consisting of 8 parts of resin (colophony) with 

 1 of linseed oil, and fusing at 97°. But the films were always 

 found after a few hours to have broken by contraction. 



Mach \ has obtained films upon a tetrahedral frame of 5 cen- 

 tims. side dipped in fused resin. He has also obtained films 

 from solutions of alkaline silicates which hardened on exposure 

 to the air. 



M. Plateau § has found a mixture of 5 parts of resin with 1 

 part of gutta-percha superior to resin alone. A system of 

 films upon a cubical frame of 5 centims. side, prepared by M. 

 Donny, was preserved for two years, but ultimately fell into 

 fragments. 



3. The author's first experiments were made with pure 

 amber-coloured resin fused. The resulting films were brittle 

 and of irregular thickness. When 10 per cent, of turpentine 

 was added, the liquid was too mobile at high temperatures to 

 form films, and at low temperatures too stiff to form them re- 

 gularly. 



A mixture of pure resin with Canada balsam was tried, 

 with good results ; and a series of experiments followed, to 



* Plateau, op. cit. vol. i. p. 233, § 141. 



t Die Gestalten der Flussigheiten. Prag. : 1872. See also Plateau, op. 

 cit. vol. ii. p. 374, § 210 bis. 



X Wiener akademischer Anzeiger, 1862, vol. xlvi. 2nd part, p. 125, 

 " Ueber die Molecularwirkung der Flussigkeiten." 



§ Op. cit. vol. ii. p. 119, § 314. 



