“Upon my word, the major has provided most liberally for our entertainment!” exclaimed Mr. Seymour, as he ascended the steps which led to the platform. “I declare there is a forest of _rockets_! and what magnificent _Pin-wheels, Tourbillions, Marroons, Pots des Aigrettes, Gerbes, Courantins, and Roman Candles_.” “Are those paper cylinders, with long sticks, rockets?” enquired Tom. “They are; and if you will attend to me, I will explain the principle of their construction. They have ever been considered as holding the first place amongst single fire-works, and deservedly so; not only on account of the splendid appearance they present when fired by themselves, but from their extensive application in increasing the beauty of other exhibitions. The rocket, you perceive, consists of a strong paper cylinder, which is filled with a suitable composition; it is crowned with a head, or ‘_pot_,’ as it is technically termed, charged with various materials, which throws out sparks, stars, and other decorations, as soon as it takes fire in the air, after the body of the rocket has been consumed. You may observe that the head is made to terminate in a point, which greatly facilitates its passage through the air. The whole is affixed to a straight stick, which, like the rudder of a ship, makes it turn to that side towards which it is inclined, and consequently causes the rocket to ascend in a straight line.” “But, papa,” observed Louisa, “all the rockets have not straight rods; see, there is one, with a crooked stick.” “That is for the purpose of causing the rocket to ascend in the form of a screw: the first effect of the bent rod will be to make the rocket incline towards that side to which it is bent; but its centre of gravity bringing it afterwards into a vertical situation, the result of these two opposite efforts will be, that the rocket will ascend in a zig-zag or spiral form. In this case, however, since it displaces a greater volume of air, and describes a longer line, it will not ascend so high as if it had been impelled in a straight direction; but I think you will admit that, on account of the singularity of this motion, it produces a very agreeable effect.” “And what causes the rocket to ascend into the air?” asked Tom.