Lavoisier nowhere alludes to this theory of Hook nor gives the least hint that he had ever heard of it. This is the more surprising, because Hook was a man of great celebrity; and his Micrographia, as containing the original figures and descriptions of many natural objects, is well known, not merely in Great Britain, but on the continent. At the same time it must be recollected that Hook's theory is supported by no evidence; that it is a mere assertion, and that nobody adopted it. Even then, if we were to admit that Lavoisier was acquainted with this theory, it would derogate very little from his merit, which consisted in investigating the phenomena of combustion and calcination, and in showing that oxygen became a constituent of the burnt and calcined bodies. About ten years after the publication of the Micrographia, Dr. Mayow, of Oxford, published his Essays. In the first of which, De Sal-nitro et Spiritu Nitro-aëreo, he obviously adopts Dr. Hook's theory of combustion, and he applies it with great ingenuity to explain the nature of respiration. Dr. Mayow's book had been forgotten when the attention of men of science was attracted to it by Dr. Beddoes. Dr. Yeats, of Bedford, published a very interesting work on the merits of Mayow, in 1798. It will be admitted at once by every person who takes the trouble of perusing Mayow's tract, that he was not satisfied with mere theory; but proved by actual experiment that air was absorbed during combustion, and altered during respiration. He has given figures of his apparatus, and they are very much of the same nature with those afterwards made use of by Lavoisier. It would be wrong, therefore, to deprive Mayow of the reputation to which he is entitled for his ingeniously-contrived and well-executed experiments. It must be admitted that he proved both the absorption of air during combustion and respiration; but even this does not take much from the fair fame of Lavoisier. The analysis of air and the discovery of oxygen gas really diminish the analogy between the theories of Mayow and Lavoisier, or at any rate the full investigation of the subject and the generalization of it belong exclusively to Lavoisier.