GLOBES AND BALLS. 237 



of ivory, and 8 pounds of saw-dust previously boiled in a solution 

 of saltpetre, and dried in the shade, or in the sun. 



Or, to 2 pounds of bruised gunpowder, add 12 pounds of salt- 

 petre, 6 pounds of sulphur, 4 pounds of iron filings, ind 1 pound 

 of Greek pitch. 



It is not necessary that this composition should be beaten so fine 

 as that intended for rockets : it requires neither to be pulverised 

 nor sifted ; it is sufficient to be well mixed and incorporated. But 

 to prerent it from becoming too dry, it will be proper to besprinkle 

 it with a little oil, or any other liquid susceptible of inflammation. 



SECTION II. 



Of Globes which leap or roll on the Ground* 



1. HAVING constructed a wooden globe with a cylinder, similar 

 to that above described, and having loaded it with the same com. 

 position, introduce into it four petards, or even more, loaded with 

 good grained gunpowder to their orifices, which must be well stop- 

 ped with paper or tow. If a globe, prepared in this manner, be 

 fired by means of a match, it will leap about, as it burns, on a 

 smooth horizontal plane, according as the petards are set on fire. 



Instead of placing these petards in the inside, they may be 

 affixed to the exterior surface of the globe ; which they will make 

 to roll and leap as they catch fire. They may be applied in any 

 manner to the surface of the globe. 



2. A similar globe may be made to roll about on a horizontal 

 plane, with a very rapid motion. Construct two equal hemispheres 

 of pasteboard, and adjust in one of them three common rockets 

 filled and pierced like flying rockets that have no petard : these 

 rockets must not exceed the interior breadth of the hemisphere, 

 and ought to be arranged in such a manner, that the head of the 

 one shall correspond to the tail of the other. 



The rockets being thus arranged, join the two hemispheres, by 

 cementing them together with strong paper, in such a manner that 

 they shall not separate, while the globe is moving and turning, at 

 the same time that the rockets produce their effect. To set fire to 

 the first, make a hole in the globe opposite to the tail of it, and in. 

 troduce into it a match. This match will communicate fire to the 

 first rocket j which, when consumed, will set fire to the second by 

 means of another match, and so on to the rest ; so that the globe, 



