He also illustrates two ordinary rockets mounted on a centre similar to that of a double saxon. This he calls “baton à feu,” and describes that one case lights after the other is burnt out, and one gathers that the device is intended to revolve but how it can be made to do this by fire issuing radially is not apparent. The word tourbillion is the French for a whirlwind and is applied by Ruggieri to a compound firework, which will be considered later under that head. What we know as tourbillion he names “fusée de table” (a table rocket), and adds that they are commonly called “artichauts.” The success of all the above, in common with rockets, depends on careful and experienced construction and strength of the case, and it is indeed curious that Jones describes the rolling of the cases for these fireworks without paste except on the edge of the paper. It seems incredible that an experienced pyrotechnist should make such a mistake, and one is almost inclined to agree with Kentish (1878), who says of Jones’s book: “The greater portion of it is absurd and impracticable, and shows it was written by a person who undertook to teach what he had not learnt.” Nevertheless Jones’s book, as Kentish says, has been copied by almost every book published since, just as his own matter was largely pirated from previous works. In fact, for a century and a half the plates illustrating pyrotechnic works were in a great degree fac-similes of one another. The catherine wheel, or, as it is sometimes called, the pin wheel, is a rotating firework of simple, as distinct from compound construction, and should therefore be included in this class. It consists of a long, thin case of small diameter, charged with a composition of sulphur, saltpetre, and mealed gunpowder. This case is wound round a circular block of thin wood, with a hole in the centre through which a pin or nail is passed, forming a pivot upon which the wheel turns. The case of the catherine wheel, unlike any firework we have considered up to the present, burns down as the composition is consumed, and for this reason it may be included equally well in another small class of fireworks. This class includes the lance, the port-fire, the starlights, feathers, and the colour cases used on wheels and saxons, etc. The lance is used in display work in greater numbers than any other unit. Some idea of the quantity used may be gathered from the fact that on one of the battle set pieces shown at the Crystal Palace as many as thirty thousand lances are consumed in a single display. Lances consist of thin paper cases about the diameter of a lead pencil, filled with colour composition, and primed, to facilitate the lighting, with mealed powder damped with water. This sets and further serves to retain the contents of the lance, which are not compressed solid as are fountains, rockets, etc.