280 Mr Sang on the Theory of Capillary Action 



the bell-glass is shut either with a stopper, or also, as repre- 

 sented in the figure, is covered with a smaller bell-glass. If we 

 wish access to the evaporating dishes, we remove the stopper or 

 the small bell-glass, raise the large bell-glass, and in an oblique 

 direction, in order to prevent the splashing of the sulphuric 

 acid) and place it in the mean time in an empty dish, with the 

 side supported against its rim. I have also found that the tube 

 may be left open, and still the evaporation goes on well, because 

 the dry air in the bell-glass is, as is well known, heavier than 

 the moister exterior air, and thereby the intermixture of this 

 latter is in great part prevented. When tubulated bell-glasses 

 are not to be had, we can use in place of them large flasks 

 with straight sides, the bottoms of which are cut off*. 



By means of this apparatus, I have succeeded in producing 

 not only well formed crystals of the new compounds already 

 mentioned, but also distinct shoots of combinations of substan- 

 ces, which were held to be partly incapable of crystallization, 

 or had hitherto been known only in confused forms. 



Observations on the Theory of Capillary Action given in the 

 Supplement to the Encyclopaedia Britannica. By Edward 

 Sang, Esq. Teacher of Mathematics. Communicated by 

 the Author. 



An the article Capillary Action, inserted in the Supplement 

 to the Encyclopaedia Britannica, it is assumed, as the basis of the 

 theory, that the attraction existing between the particles of mat- 

 ter extends only to distances which are insensible when com- 

 pared with the extent of capillary action. And, in order to ex- 

 plain the elevation of a fluid at the sides of a partially immer- 

 sed solid, we are told, that the attraction of the solid (K' — ^ K) 

 first causes the elevation of the adjacent film, that this film then 

 acts as a second solid, raising that immediately adjoining, and 

 that thus the disturbance extends to the entire surface of the 

 fluid ; nor docs the author stop short here, for he assumes that 



• The best mode of cutting off the bottom of flasks is to tie round them 

 a cord dipped in oil of turpentine, and then set fire to it. 



4 



