344 REPORT — 1851. 



a* is a brass cap soldered to A. 



a^ is part of a small vent (or cock) opening into A. 



a^, a tube (of the vent) with a small aperture at the pointed end, which 

 when turned downward, permits fluid (above the opening of a^ into A) to 

 pass out, but when turned upwards that opening is entirely closed. By these 

 means it is easily ascertained when aether enough has been poured into A. 



a* is a stop-cock communicating with A and D, and serving as a support 

 for A, &c. 



B is the immersed thermometer, the tube of which passes (with cement) 

 through a little pipe soldered to a disc (not shown) which rests upon a flange 

 in a'. 



b', a ring (with milled edge) screwed upon a', and serving (with a leathern 

 washer) to press the disc (carrying B, &c.) firmly down upon the flange in a'. 



C is a pipe for admitting air (and also for feeding A with aether) on oc- 

 casion ; it passes through the above-mentioned disc (with cement), and ex- 

 tends nearly to the solid glass cylinder in the bottom of A. Its upper end is 

 funnel-shaped. When the instrument is not in use, this end is closed by a 

 milled-headed stopper and leathern washer (to prevent the escape of aethe- 

 rial vapour). 



D is a brass column having a cylindrical bore throughout its length, ex- 

 cepting the upper plane of the cube ; a* is screwed into the cube and com- 

 municates with the bore. 



A glass shade may be placed over A, D, &c., for protection from rain, 

 dust, &c. (on occasion). 



E, figs. 2 and 3, is the aspirator. 



e' is a pipe fitted into the bore of D, and entering 



eS which is a square piece perforated horizontally and ground to fit 

 exactly upon 



e', which is a tube, closed by plugs, at its left end and its central part (in 

 the manner shown in fig. 3). A perforation through the (always) upper side 

 of e^ and through e* admits a free passage of air, setherial vapour, &c. from 

 e' into e^. 



e* is a squared piece perforated horizontally, and ground to fit exactly 

 upon e^, but having liberty to revolve upon e^ on occasion. 



e^, a pipe entering e*, and norv ascending from it. Another perforation 

 through the (always) upper side of e^ admits a free passage of air from e^ to 

 e' when e* is in the position shown. 



e'^ is a rectangular vessel into which e* opens, very near to its now upper 

 surface ; and e* is soldered at the place where it passes through the now 

 lower surface of e^. 



e'^, a pipe opening at a small distance from the now interior bottom of e^, 

 and from the now interior top of 



e^, which is a vessel exactly similar to e^. 



e^ is a pipe opening into the now upper part of e^, and entering 



e'°, which is a squared piece perforated horizontally to fit upon e^, but 

 having liberty to revolve upon e^ when necessary. A third perforation 

 through e^, at its always lower side, and through e'°, admits a free passage 

 of air from e^ to e^. 



It is evident that if e^, in its present position, should contain water, and 

 that if a current of air were permitted to flow through e', through the left- 

 hand hollow part of e^, and through e\ the water would descend through 

 e', and air, in e°, would escape through e^, and through the right-hand end 

 of e^, or (vice versa) that the descent of water from e^ to e^ (through e') 



