218 COMPOSITION OF ROCKETS. 



that number in the column of pounds, and opposite (o it, in the 

 column of calibres, will be found the number 2K8. Then say as 

 100 is to J9{, so is 288 to a fourth term, which will be the 

 number of lines of the calibre required ; or multiply the number 

 found, that is 288, by 19j, and from the product 56"' 16, cut off the 

 two last figures: the required calibre therefore will be 56-16 lines, 

 or 4 inches 8 lines. 



On the other hand, the calibre being given in lines, the weight of 

 the ball may be found with equal ease : if the calibre, for example, 

 be 28 lines, say as I0[ is to 28, so is 100 to a fourth term, which 

 will be 143*5, or nearly 144. But in the above table, opposite to 

 144, in the second column, will be found the number 3 in the first ; 

 which hews that a rocket, the diameter or calibre of which is 28 

 Jiues, is a rocket of a 3 pounds ball. 



CHAP. II. 



COMPOSITION OP THE POWDER FOIl ROCKETS, AND THJt 

 MANNER OF FILLING THEM. 



J. HE composition of the powder for rockets must be different, 

 according to the different sizes ; as that proper for small rockets, 

 would be too strong for large ones. This is a fact respecting which 

 almost all the makers of fire-works are agreed. The quantities of 

 the ingredients, which experience has shewn to be the best, are as 

 follows : 



For rockets capable of containing one or tiso ounces of com. 



position. 



To one pound of gunpowder, add two ounces of soft charcoal ; 

 or to one pound of gunpowder, a pound of the coarse powder used 

 for cannon ; or to nine ounces of gunpowder, two ounces of char, 

 coal ; or to a pound of gunpowder, an ounce and a half of saltpetre, 

 and as much charcoal. 



For rockets of tzco or three ounces. 



To four ounces of gunpowder, add an ounce of charcoal j or to 

 nine ounces of gunpowder, add two ounces of saltpetre. 



