10 



Ne7V inusfration of 



M 



D. S. Holman, of 



Philadelphia, has recently devTsed a very neat and simple apparatus, 

 useful to teachers, whereby the method of formation of cells in veg- 

 etable structure may be conveniently shown to an audience. It con- 

 sists merely of a tank formed of two pieces of plate glass, held apart 

 at the. bottom and sides by a rubber strip and kept in place by four 

 clamps. Into this receptacle is poured a solution of soap, which is 

 raised m bubbles by a current of air blown into it through a fine glass 

 tube. As the bubbles are formed, their tendency to become spheres 

 IS overcome by the capillary attraction of the sides of the tank. As 

 a natural consequence, the films extend across the tank perpendicular 

 to the walls and the pressure of one bubble upon another causes the 

 Iormation_ of polygonal forms, analogous to those which we see in 

 cross-sections of wood-fibre. The accompanying figure, which we 





Jour?Hil of the F. 



the appearance presented by the tank when thus filled with bubbles 

 but gives no conception, it is said, of the beauty of the projection of 

 which maybe made upon a screen. The pencil of ^ay\ passing 



from the condensmg lens of a stereopticon is convergent ; and a a 

 conseniienrp mnnv ro,.c r^n ,.w *u i-i &^ '*-? ^'^\^'^y <^^ ^ 



consequence, many rays fall upon the soap films at such a large in- 

 cident angle that they are almost entirely reflected, and conseoiiertW 

 are tinged with the rich colors resulting from the interference of lie 

 rays that fall on thin films. We thus^have beLe us a p oof o 1 e 

 tenuity of a layer which is between the limits of i-i oooth and - - 

 ooothof an inch-the latter limit being reached when the color of 

 the film disappears. The same illustration also a Jrds an exempli 

 fication of the principle (shown in Nature In the structure ofSe 

 honey-comb) that the pressure of equal circles on each o her pro^ 

 duces a hexagonal structure. P 



Cornell University.— \\^ learn from the daily papers that the Bo 

 tanica Department of Cornell University has rec^en^tly been the re' 

 7ithlca ' "''' "' ^'" ^^^^"^"^^ ^^"-^ '-- ^^^ Hon' H V Sage; 



