^4> BXHArSTINCf MACHIIfB. 



is supported by the wooden pillars H. Tlie surface of th<?^ 

 plate is to be ground perfectly flat. B is an iron tube, ce- 

 mented at its upper extremity in a hole drilled in the plate 

 A, and having its lower extremity terminated at the bottom 

 of the wooden tub E, by a stop cock, which is opened aiid 

 shut by the wire F. The length of the tube ought to be 

 about three feet; its diameter about the size of a common 

 barometer tube. 1 he receiver is to be ground in the usual 

 manner to the plate, and to be fitted with an air-tight cover, 

 I, ground to its upper oriiice. ILis a stop cock, through 

 which the external air may be admitted when required. A 

 slight depression ought to be made in the glass plate about 

 one inch around G, that the mercury may more readily de- 

 scend through the tube. The iron tube ought to reach 

 through the glass plate to the bottom of the slight depres- 

 sion ; and its inside at the top is to be furnished with a fe- 

 male screw, by which the transferrer, or any other appara- 

 tus to be used within the receiver, raay be fixed to the 

 plate. It is hardly necessary to observe, that the piece of 

 iron which screws into the upper end of the tube B must 

 be so perforated, as to permit the easy descent of the mer- 

 cury. The inside of the tub E ought to be coated with 

 strong varnish, to prevent the loss of mercury through its 

 joinings, and may have a cover so fitted to it, as to keep 

 out dust, though not to exclude air. The lower extremity 

 of the tube B ought for steadiness to be fixed to the bot- 

 , torn of the tub, by a flanch and screws. The edges of C 



ought to project about tvvo inches above the glass plate, that 

 any mercury which falls over may not be lost. 



The transferrer, fig. 2, is made like the plate A, and 

 frame C, fig. 1. The lower rim of u is intended to rest 

 upon the edges of C,' when the iron screw b is fixed in G. 

 The key of the stop-cock, d, passes through the lower rim, 

 as in the figure. 

 Metfeodofus- To use the exhausting machine, draw off the mercury 

 ing ihenia- which is in the tub E, bv the stop-cock L, leaving iust as 

 nmuch as will cover the extremity of the iron tube. Shut 

 the stop-cock at M, pour in mercury at G to fill the tube, 

 anoint the glass plate with hog's lard, place on the receiver, 

 fill the receiver likewise with mercury, and then place it* 



cover 



