838 AERIAL GLOBKS. 



if placed on a smooth horizontal plane, will be kept in continual 

 motion. 



It is here to be observed, that a few more holes must be made in 

 the globe, otherwise it will burst. 



The two hemispheres of pasteboard may be prepared in the fol- 

 lowing manner : construct a very round globe of solid wood, and 

 cover it with melted wax ; then cement over it several bands of 

 coarse paper, about two inches in breadth, giving it several coats of 

 this kind, to the thickness of about two lines. Or, what will be 

 still easier and better, having dissolved, in glue water, some of the 

 pulp employed by the paper makers, cover with it the surface of 

 the globe ; then dry it gradually at a slow fire, and cut it through 

 in the middle ; by which means you will have two strong hemi. 

 spheres. The wooden globe mav.be easily separated from the paste- 

 board by means of heat; for if the whole be applied to a strong 

 fire the wax will dissolve, so that the globe may be drawn out. 

 Instead of melted wax, soap may be employed. 



SECTION III. 



Of Aerial Globes, called Bombs. 



THESE globes are called aerial, because they are thrown into 

 the air from a mortar, which is a short thick piece of artillery of a 

 Jarge calibre. 



Though those globes are of wood, and have a suitable thickness, 

 namely, equal to the twelfth part of their diameters, if too much 

 powder be put into the mortar, they will not be able to resist its 

 force ; the charge of powder therefore must be proportioned to the 

 globe to be ejected. The usual quantity is an ounce of powder for 

 a globe of four pounds weight ; two ounces for one of eight, and 

 so on. 



As the chamber of the mortar may be too large to contain 

 the exact quantity of powder sufficient for the fire ball, which 

 ought to be placed immediately above the powder, in order that it 

 may be expelled and set on fire at the same time, another mortar 

 may be constructed of wood, or of pasteboard with a wooden bot- 

 tom : it ought to be put into a large iron mortar, and to be loaded 

 with .1 quantity of powder proportioned to the weight of the globe. 



This small mortar roust be of light wood, or of paper pasted to. 

 getber, and rolled up iu the form of a cylinder, or truncated cone, 



