342 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



changes of color produced in the different ends of the solu- 

 tion ; it being reddened on one side, and rendered green at 

 the other. Price, with binding screws, $1.75. 



" without " $1.25. 



Fig. 407. 



The Powder Cup. (Fig. 407, as above.) This consists 

 of a glass having a neck through which the ends of two 

 wires, insulated from each other, are passed, and are con- 

 nected together within the cup by a fine platina wire. On 

 connecting the long ends of the wires with the poles of a 

 galvanic battery, the passage of the current heats the fine 

 platina wire to redness, and explodes any powder placed in 

 the cup. A piece of sulphur or phosphorus may also be 

 easily burned therein. Price, 80.50. 



Fi s- 408 - The Galvanic Gas Pistol 



(Fig. 408.) This instrument 

 is constructed on the same 

 principle as the last described, 

 but arranged in the form of a 

 pistol, the wires being fastened through a brass plug which 

 screws into the barrel. To use, the pistol is filled with 

 from one third to one half of hydrogen gas, the other part 

 being atmospheric air, and corked ; connect one of the wires 

 with one of the poles of a galvanic battery, and on bringing 

 the other wire in contact with the other pole of the battery 

 the wire will be heated to redness, and the gas exploded. 



Price, $3.00. 



