CHEMICAL APPARATUS. 



95 



Fig. 557. 



is connected with a cord, which passes round a wheel on 

 the centre of an index, to another lever on the opposite side, 

 intended to balance the first lever. Over these levers are 

 springs, to keep the cord tight. The index and wheel on 

 which the cord moves is fixed to an upright support, having 

 a graduated brass ring, divided, and numbered on its face 

 from to 360. A rod of any metal, the expansion of which 

 is to be tried, is put between the point of the screw and 

 the lever, as before described, and as soon as 

 the heat of the spirit lamps beneath is applied 

 the metal will begin to expand, and its com- 

 parative degree of expansibility will be shown 

 by the distance to which the index moves, as 

 noted on the graduated circle. In comparing 

 different metals with this, it will be necessary to 

 make the rods of the same size, and apply the 

 heat of the lamps the same length of time. 



Price, $3.50. 



Fire Syringe. (Fig. 556.) This instrument 

 is used for procuring an instantaneous light, by 

 means of the condensation of air. It consists 

 of a stout condensing syringe, having a solid 

 piston with a hole, for containing a small piece 

 of tinder, at the end. Upon forcing down the 

 piston quickly, the air within the tube 

 is rapidly condensed, and the conden- Fig. 556. 

 sation occasions so great an evolution 

 of heat as to light the tinder. 



Price, $1.00. 



A larger and more elegant article 

 (Fig. 557) with glass cylinder for 

 showing the flash of light accompany- 

 ing the ignition. Price, $6.00. 



Caloric conducted slowly by Fluids 

 downwards. (Fig. 558, next page.) 

 This apparatus, to show that caloric 

 is conducted by fluids slowly in a 

 downward direction, consists of a fun- 

 nel-shaped glass vessel, having an air 

 thermometer, with a ball of consider- 



