Frézier shows a wheel similar to that given by Babington, and variations on the double saxon, a fixed sun also, as do most early writers, double line rockets to run backwards and forwards and variations. These latter, which appear to have been very popular at this period, were known in France as “courantins.” Bate calls them “swevels,” other early writers “runners on the line.” The above-mentioned, together with some rather intricate but impracticable appearing water devices, make up the compound fireworks in Frézier’s book. It seems, however, that he must have been behind his day in this branch of the art, as the Aix-la-Chapelle peace display appears to have included several elaborate pieces which, even allowing for the usual exaggeration of the programme, must have required considerable skill and knowledge in construction. These were mostly what were called regulated or regulating pieces, generally described as of a certain number of mutations. The pieces were, and are, although the old descriptions are now dispensed with, so constructed that after being lit they go through a series of alterations in form and movement without further attention. Some of those described in old works would seem to have required more than a slight element of luck for their successful performance. To-day it is often found more advantageous to make a second lighting in cases where there is a danger of premature ignition, the effect to the spectators being identical, and the successful functioning of the piece secured. This does not apply to all pieces of this nature, as with modern safety fuse the pyrotechnist has considerable advantage over the earlier practitioners. The modern spectator is only concerned with the effect produced, not by the means adopted to produce it. It is difficult to-day to realise the position occupied by the pyrotechnist of the eighteenth century. He carried out his work personally, with of course trained assistants, and occupied a position similar to the artist or sculptor. Each piece was looked upon as a work of art, the personal effort of the pyrotechnic artist. Ruggieri gives some idea of this in the following passage from his book: “It was in the month of July, 1743, that my father and my uncles Ruggieri exhibited for the first time at the Theatre de la Comédie Italienne and before the King, the passage of fire from a moving to a fixed piece. “This ingenious contrivance at first astonished the scientists of the day, who said when it was explained to them that nothing could be more simple and that any one could have done it at once.” He then explains the method of construction, which is to lead from the back end of one of the turning cases through the hollow centre of the axle to the lighter of the fixed piece situated behind it. The development of fixed and mechanical pieces was made possible by the introduction of quickmatch.