DEMONSTRATIONS IN PHYSICS 



K, is fixed by the screw m 2 the 

 ring E, which carries the focus- 

 sing objective, bearing at the top 

 another ring /, carrying the in- 

 clined mirror s 2 , which reflects 

 the image to the screen. 1 



119. Viscosity. Very im- 

 pressive experiments may be pro- 

 jected with a 2 per cent, solution 

 of saponine. With care this will 

 blow a bubble nearly 2 inches 

 diameter ; the best way is to clip 

 a small glass funnel f inch dia- 

 meter mouth downwards in a 

 universal holder, with a bit of 

 rubber tube for blowing sprung 

 on the small end ; this is adjusted 



W 



1 For details of these experi- 

 ments and their practical manage- 

 ments cf. Taylor's Memoir, xiii. 

 and xxi. ; Phil. Mag., xiv. 1, xvi. 

 23, xxii. 286. In America, details 

 may be found in Smithsonian 

 Reports, 1865, p. 207. Three lec- 

 tures by Mr. C. V. Boys on Soap 

 Bubbles (S.P.C.K. 2s. 6cZ.) are 

 published just as these pages go 

 to press, and describe other attrac- 

 tive projection experiments in 

 this branch of physics. 



FIG. 116. Platen's Experiment 



Q2 



