598 F. W. GAMBLE AND F. W. KEEBLE. 



wide bore and of stoat glass; it is connected with the main 

 tank in the Piel Laboratory, from which the bottle can be 

 filled in about one minute. A second tube {h), the pressure- 

 tube, passing down almost to the level of the exit-tube, 

 serves, when the apparatus is working, to give the aspirator 

 the action of a Mariotte's bottle, — that is to say, to maintain 

 the rate of flow approximately constant (see F. F. Blackman, 

 'Trans. Roy. Soc./ 1895). 



To this tube is connected a series of glass flasks, through 

 which air entering the aspirator must pass (see Fig. 1, B 

 and C). The exit-tube, fitted into the lateral tubulure of 

 the aspirator, is at its commencement (x) of a very fine bore, 

 and connects on by its wider end, which projects beyond the 

 aspirator, with the first of our series of '^ water-circulator " 

 dishes (D and E) . Each " water-circulator " is made of a 

 glass dialyser frame having the form of a low cylinder, open 

 above and below and provided with a lateral tubulure. To 

 the bottom rim of this dialyser a glass plate is affixed by 

 means of suitable wax. The exit-tube from the aspirator 

 is connected with another passing through the cork in the 

 tubulure of the dialyser, and so bent as to follow the curved 

 side of the dish, in order that the water which it conveys 

 may enter the dish at a point opposite the tubulure, and 

 so be constrained to circulate before making its exit. 



Through a second hole in the cork a glass tube just pro- 

 jects into the dish, and serves to carry the water to a second 

 similar " water-circulator,'^ whence it flows to a third. To the 

 upper rim of each "water-circulator" a glass plate ground 

 at its edges has to be fixed. From the last of this series 

 the exit-tube discharges the water which has circulated 

 through the series. 



To prepare the apparatus for action, the aspirator is filled, 

 a wide tube (the escapement-tube) just projecting through 

 the cork of the neck being opened to allow the air to escape. 

 The aspirator being full this tube is closed ; the " air-circu- 

 lator " flasks (the arrangement of the tubes of which will be 

 I'eadily understood by reference to Fig. 1) are filled to a 



