In all the great diversity of fireworks that has been developed, the rocket still maintains its supremacy. It is today manufactured in various forms and equipped with distinctive garnitures adapted individually to serve a vast number of purposes. Its importance is by no means limited to its spectacular effect, designed for pleasant entertainment to the beholder, but it is of an impressive practical value in certain phases of its employment as the. instrument of signaling or of direct illumination. As its utility in such directions has advanced, so its construction has been perfected, and the intensity of its effect has been magnified to an extraordinary extent. The largest sizes are now provided with lights of utmost brilliancy, which are supported by parachutes proportioned in size.

The general principles governing the construction of rockets have remained unchanged. The only present variation is in the matter of details. The most interesting variation in the present methods from those of the past has to do with the air chamber, or the "soul of the rocket," as it is still called in French and Italian. There have been alterations as to this cavity, both as to its dimensions and as to the means employed in making it. Where formerly the case was loaded on a spindle, by which a conical empty space was secured inside the charge, the present fashion prefers a solid loading of the case without use of a piercer, and the subsequent boring of the charge from the bottom, in order to secure the required air chamber. In this case, the opening is made by means of a gage which has a sharp, curving cutting end, with a shaft somewhat smaller in diameter and of a length appropriate to the size of the rocket. By the use of this tool, a cylindrical opening is made within the charge, which extends to the required distance. Of course, during this boring process, care must be exercised to avoid any overheating of the tool, which might kindle the charge. The usual measurements for the air chamber made in this manner give it a diameter one-third that of the interior diameter of the case and a length two-thirds that of the charge. This method is followed generally in the manufacture of small rockets and those of medium size. It is not, however, employed in the making of large rockets. The rockets of smaller size are loaded merely with powder, and a subsequent making of the cavity offers little danger. Frequently, too, where a more striking effect is desired, ease in the making is secured by loading the case for two-thirds its height with powder, and then completing the charge with a livelier mixture. This compromise method permits a reasonably safe boring.

While various facts, long ago determined, as to the proper relative weights of garniture and rocket remain essentially undisturbed, the rule now is that the garniture shall not exceed one-third the weight of the rocket.

So, also, the balancing point of the rocket remains about the same, and the usual proportion of the stick's length is about twelve times that of the rocket.

While powder of an ordinary sort has sufficient force for giving flight to a small rocket, a special mixture is demanded for the rocket of larger caliber.

Three formulas for such compositions are as follows:

Powder .................................................................................

1G

Niter ..................................................

4

Sulphur ............................................................................................

1 1/2

Charcoal (hard wood) ........................................................

4

Powder ....................................................................................

33

Charcoal (hard wood)_____________________________

2

Or the charcoal may be reduced to one and one-half.

Powder......................

16

Niter.....................

10

Sulphur.....................

2 1/2

Charcoal (hard wood).....................

6

Of the above formulas, the first and second may be properly used for rockets of medium size, but the third is designed exclusively for large rockets.

Formulas for the brilliant fire to be used in loading large rockets are as follows:

Powder ...........................

16

Niter........................

1

Sulphur......................

1

Steel filings.......................

5

Powder ....................

24

Niter.................

5

Sulphur.....................

13

Steel filings.......................

5 1/4

Charcoal (soft wood).................

19

The following formula is used to secure the effect of Chinese fire:

Powder.......................

15 1/4

Niter.................

10

Sulphur..................

5

Cast-iron filings......................

5

The mixtures indicated above are commonly used for the upper third of the charge, while the lower two-thirds is of powder and charcoal, loaded solidly and afterward bored. This method is followed especially in the manufacture of medium-size rockets, and the change in the spectacle, offered as the fire passes from the first part of the charge to the second, produces an agreeable effect. Such Contrast is often emphasized by added variations between the two mixtures.

The garnitures with which rockets are equipped are almost endless in the diversity of their forms, but the innumerable variants are all derived from sources with which we are already thoroughly familiar from our historical examination of the subject. In addition to the different garnitures, the rockets themselves are often combined so that a number are united in their flight to form a distinctive display, regulated by their arrangement and the manner of their discharge, which may be either simultaneous or in sequence, according to the distribution of the fuses.

There has been no notable change in the principles governing the construction of table rockets, which are still unfailingly popular for their pleasing effects of light and movement directed by the disposition of the fuses. Powder alone suffices for the loading of small table rockets. For those of larger size, charcoal is added.

Powder.................

16

Charcoal ......................

3

For a sparkling-fire effect:

Powder......................

16

Steel filings.............................

3

Either of two formulas may be employed to produce Chinese fire:

Powder........................

16

Niter..........................

2

Sulphur............................

1

Charcoal.......................

1

Cast-iron filings..............................

2

Powder..................

8

Niter..........................

2

Sulphur................................

1

Cast-iron filings.............................

3