212 



BENJ. PIKE S, JR., DESCRIPTIVE CATALOGUE. 



this experiment, and in all others where mercury is used, 

 great care must be taken to prevent the introduction of any 

 mercury into the air pump, as it would cause considerable 

 njury. Price, $1.00 ; receiver, Tocts. 



Shower of Mercury Tube. (Fig. 213.) This 

 consists of a glass tube, about one and a half inch 

 in diameter, and from twelve to twenty-four inches 

 long, with a cap and screw at one end, fitting the 

 air pump on the inside, having a small glass tube 

 with a hole at the side, for preventing the mer- 

 cury being drawn into the pump, and at the top 

 of the tube a hard wood cap, within which a 

 piece of oak wood is supported, having a funnel 

 or cap of hard wood screwing over it, into which 

 the mercury is placed ; on exhausting the tube 

 by the air pump, the mercury will pass through 

 the pores of the wood, and descend into the tube 

 in a silver shower. 



Price, $4.00 and $5.00. 



Fig. 214. Flask for Weighing Air. 



Fig. 214 consists of a glass 

 flask or globe, having a cap 

 and stop-cock fitting the air 

 pump, supported by a hook to 

 a scale beam. To use, first 

 weigh the flask of air, as re- 

 presented in the cut, by plac- 

 ing the requisite weights in the 

 scale pan ; then exhaust the 



flask of air by the air pump, and weigh it again in the same 

 manner ; the difference in the weights will give the weight 

 of air, or gas taken out. 



Price, flask with stop-cock, 



" mounted with steel beam and stand, $6.00. 



