In this work Chertier devotes most of his attention to the subject of colour, and although new ingredients have been introduced which were either unknown or were not then available on account of expense or other causes, since the time of his writing, yet there can be no doubt that Chertier stands alone in the literature of pyrotechny and as a pioneer of the modern development of the art. Tessier, in the introduction to his “Treatise on Coloured Fires,” published in 1859, whilst paying tribute to Chertier’s work, regrets that he only possessed “quite superficial notions of chemistry.” Here speaks the chemist. The writer recently asked a pyrotechnic chemist of many years’ experience, whose knowledge of pyrotechnic chemistry is probably second to none, his opinion of Tessier’s book, and received this answer. “Tessier’s book contains too much chemical theory and too little pyrotechnic practice.” There speaks the pyrotechnist. The writer, as he has before remarked, has no wish to belittle the value of the chemist’s work in relation to pyrotechny, but a knowledge of chemistry is not the most important attribute of the successful pyrotechnist. As in other arts so in pyrotechny, experience and natural aptitude are the first essentials. Chertier may have had little knowledge of chemistry, but in spite of or perhaps because of his lack of chemical knowledge, he was able to produce a work which, from the point of view of the practical pyrotechnist, has never been equalled. His researches were conducted by practical experiments; he had one end in view, namely, pyrotechnic effect, and by exhaustive trials of the materials obtainable, unbiased by theoretical consideration, he succeeded in advancing the art to a stage undreamed of a few years previously. It is true that many of his formulæ are not in use to-day, in this country that is, on account of the danger of using sulphur or sulphur compounds in conjunction with chlorate of potash; but there can be no doubt that his writings and research work laid the foundation of modern pyrotechnic practice. Once the theory of colour production was established, that is to say the volatilisation of a metal salt in a hotly burning composition, it was a matter of less difficulty to either eliminate the sulphur, which was present chiefly as a burnable, or to replace it. This prohibition, as we have seen, took place in 1894, under Order in Council 15, and affected the production of coloured fireworks far less than might have been anticipated. During the period between the introduction of chlorate of potash and the Order in question, the development of commercial chemistry had increased greatly the number of chemicals available in pyrotechny, so that in some few cases it was found possible to replace the chlorate.