Smoke balls from 4⅖th inches up to 13 inches calibre were included in the official list of projectiles for smooth-bore guns until about 1873, when with ground light balls they became obsolete. The latter, as their name suggests, were intended to be burnt on the ground and light up enemy working parties, etc. This also was the object of the parachute light-ball, which was fitted with a time fuse and an opening charge; upon opening, a light was ignited suspended from a parachute. This method appears to have been invented in Denmark in 1820, and they were used in Austria the following year. Another class of war store which naturally suggests itself is that used to give light for the purpose of signalling. The light is either burnt on the ground as a hand light or fitted to a rocket. Fireworks for this purpose have been in use from earliest times, being the logical development of the signal beacon, but it was not until the introduction of genuine colour—that is to say, colour distinguishable at a long distance—that they reached their full standard of utility. It is, however, the rocket which has received most attention for military purposes, and certainly with good reason. Here was a projectile which, in the days of smooth-bore ordnance had a good range and required no heavy gun or transport. Moreover, it formed its own time fuse. Congreve wrote: “Rockets are ammunition without ordnance, the soul of artillery without the body.” Many methods of fitting up rockets for warlike purposes have been evolved, invented and re-invented, most of which for practical purposes were useless. It is the military use of the rocket, however, which presents the most interesting study in military pyrotechny. There are several early references to what is supposed to be the use of rockets in warfare. The Paduans are stated to have burned the town of Mestre with these projectiles. Orleans used rockets in its defence in 1429, and Dunois fired them in 1449, when besieging the town of Pont-Andemer. In 1452 they were used against Bordeaux, and the following year at Gand. Rockets were employed in 1586 for lighting purposes and as projectiles against cavalry. The description seems to indicate a method of fitting up to produce a similar effect to a shrapnel shell. Hanselet, writing in 1630, refers to rockets with grenades attached. Casimir Siemienowitz, Lieut.-General of the Ordnance to the King of Poland, published in 1650 his “Great Art of Artillery,” which contains a treatise on fireworks both for civil and military purposes. He refers to a work on the military use of fireworks written ninety years before, and speaks of rockets up to 100 lbs. and describes their construction. A French work published in 1561, entitled “Treatise upon several kinds of War-Fireworks,” suggests a rocket case of varnished leather.