The secret of the communication of fire between different pieces was brought from Bologna into France in the year 1743 by the Sieurs Ruggiere, official artificers for the Italian crown. The pyrotechnic display given by the brothers excited great admiration, especially by reason of the skill shown in the communication of fire to various pieces in succession. The Italians were obliging enough to explain their method, as follows:
Let us imagine a fixed sun set between two turning suns on an iron axis. The first is fastened from above by a peg, which traverses a hub and axle. The other two are held by screw holes in the axis, by means of which they have as much or as little play as may be required. (Pl. X, fig. 12.)
The space between the first turning sun and the fixed sun is 6 inches and 4 lines. They are supplied with two cylinders, each 3 inches long and 2 inches in diameter, mounted on the axle. These are fastened with glue, one on the hub of the fixed sun, the other on the hub of the turning sun.
Between the two cylinders, there should be mounted on the axle a button 4 lines thick, having 1 inch of diameter. This serves to hold them apart, a distance of 4 lines one from the other. In order not to multiply parts, the button is usually added to one of the cylinders, of which it forms an integral portion, or it may be added by gluing it on.
Upon the plain surface of each cylinder, a little above the button, a circular groove should be cut, with a length of 2 1/2 lines, and an equal depth, in which a match is fastened by the use of priming. It is by these matches that the communication of fire is to be accomplished, that of one cylinder not being able to burn without giving its fire to that of the other opposite, since there are only 4 lines of distance between them. The fire is carried to one by means of a match, which, passing from the end of the last of the jets of the turning sun, kindles the match lying in the circular groove above described. This match is carried in a groove cut along the spoke. It is continued over the hub and cylinder. From this point, it communicates by its extension with the match in the circular groove opposite. It is carried thence to the throat of one of the jets in the fixed sun by a match lying in a groove made along the cylinder and over the hub to the foot of the jet. From this point the match extends out to set fire to the throat. These matches should be well covered with paper pasted over them, except in the case of those placed in the circular grooves. They are protected from sparks of fire by a tube of pasteboard, or of very thin brass, which almost entirely covers the two cylinders. In order that this shield should not hinder their movement, it is given an additional two lines of diameter. (PL X, figs. 9,13, and 20.)
The length given to the cylinders has two objects. The first is to separate the circular matches from the rims of the tubes covering them, by which sparks might be introduced. The second is to hold the fixed and turning suns sufficiently far apart so that fire can not be communicated from one to the other, which would occur if they were closer, even though the communication might be well covered.
The space between the fixed sun and the second turning sun is supplied with a like communication between the two cylinders, and fire is carried to this second sun by a match, which draws its fire from the foot of one of the jets in the fixed sun. A hole is pierced in this, in order to establish communication with the match to which it gives fire when finishing.
From this second turning sun, the fire may be conducted to a second fixed sun; and so on successively to any desired extent.