52 



Colonel Sir Almroth E. Wright 



[March 9, 



(see Fig. 11), with water above and salt solution below, the upper 

 compartment contains, as in Tube 1, only a mere trace of albumen. 

 In the lower compartment we have again, as in Tube 2, a very 

 heavy deposit of albumen drawn down against gravity. 



I have here other experiments of which I show you photographed 

 drawings. All these bring out that when strong salt solution and 

 water are brought into opposition, and we introduce such a succession 

 of obstacles as are provided by a cotton-wool plug or a wick, we get, 

 so far as the convection of fluids is concerned, the same results 

 as when we interpose a thin membrane, such as parchment paper or 



NitCl 



y. 



Fig. 12. — The left-hand beaker contains water coloured with 

 methylene-blue ; the right-hand beaker strong salt solution. The 

 beakers are connected up by two siphon (J tubes — the upper being an 

 open siphon filled with uncoloured water ; the lower a siphon plugged 

 with cotton-wool and, like the upper siphon, filled in at the outset 

 with uncoloured water. 



a film of formalin gelatine. With respect to the character of the 

 fluid there is marked difference. Where we employ macroscopic 

 pores albuminous substances are carried through ; where we employ 

 only very minute pores we filter out al])uminous substances. 



In my next experiment (Fig. 12) we have in one beaker saturated 

 salt solution and in the other water coloured with methylene-blue. To 

 maintain the fluids at the same level we connect them up with a 

 siphon filled with uncoloured water. We then esta])lish a further 

 connexion by means of a siphon filled with uncoloured water plugged 

 at the one end with cotton wool. This end goes down into the salt 

 solution, but it is only just immersed. AViien we now Avatch events — 



