108 



SCIENTIFIC AMUSEMENTS. 



doubly-perforated india-rubber bung (obtainable at the instrument 

 dealers, fig. 29). 



Fig. 55. Gas Generator. 



Obtain some lumps (not powder) of chalk, or fragments of hard 



limestone or marble, and 

 carefully drop them 

 into the bottle, so as 

 not to crack or " star " 

 the sides; insert the 

 cork in the tube, and if 

 not air-tight make it so 

 with wax, tallow, lin- 

 seed meal made into a 

 paste with a little water, 

 or such like substances 

 (a sound soft cork with 

 well-bored holes of the 

 right size, or an india- 

 rubber bung with holes 

 ready perforated in it, 



ought not to require any 

 Fig. 56. Gas Generator. guch luting to mako 



it air-tight). Mix strong hydrochloric acid (solution of hydro- 



