He examines with great acuteness and precision some of the more popular opinions entertained by tanners, and brings his science to bear very satisfactorily upon several of their processes.
The grand secret, on which the profit of the trade mainly depends, is to give the hides the greatest increase of weight in the least possible time. To effect this, various schemes have been proposed, many of which, from the ignorance of the operators, instead of promoting, have defeated the object. Different menstrua have been suggested for expediting the process, and amongst them lime-water and the solutions of pearl-ash; but, as he has clearly shown, these two substances form compounds with tannin which are not decomposable by gelatine; whence it follows that their effects must be pernicious; and there is very little reason to suppose that any bodies will be found which, at the same time that they increase the solubility of tannin in water, will not likewise diminish its attraction for skin.
His experiments having proved that the saturated infusions of astringent barks contain much less extractive matter, in proportion to their tannin, than those which are weaker, it follows, that by quickly tanning the skin, we render the leather less durable. These observations show that there is some foundation for the vulgar opinion of workmen, concerning what is technically called the feeding of leather in the slow method of tanning.
Such is an outline of this interesting paper, in which the author has displayed the talent so characteristic of his mind—that of bringing science and art into useful alliance with each other. It forms, at this day, the guide of the tanner; and those who previously carried on the process by a routine of operations, of which they knew not the reasons, are now capable of modifying it, without the risk of spoiling the result. Many of those expedients which have been brought forward as novelties in later years, may be found in this paper; or, at least, have arisen out of the principles disclosed during his investigations.
It has been stated that, shortly after Davy's successful début as a lecturer, his manners underwent a change, and that, to the regret of his friends, he lost much of his native simplicity. On the 5th of February 1802, he had dined with Sir Harry Englefield at his house at Blackheath; and eighteen years afterwards, the worthy Baronet alluded to his interesting demeanour upon that occasion, in terms sufficiently expressive of his feelings—"It was the last flash of expiring Nature." It was natural that his best friends, on perceiving this change of manner, should entertain some apprehensions as to the deeper qualities of his heart. Mr. Purkis has placed in my hands the following letter addressed to him by Mr. Coleridge; it will interest the reader by the force and truth with which its talented writer characterises the perils which beset the elevated path of the young philosopher at the commencement of his career.
TO SAMUEL PURKIS, ESQ.
Nether Stowey, Feb. 17, 1803.
MY DEAR PURKIS,
I received your parcel last night, by post, from Gunville, whither (crossly enough) I am going with our friend Poole to-morrow morning. I do from my very heart thank you for your prompt and friendly exertion, and for your truly interesting letter. I shall write to Wedgwood by this post; he is still at Cote, near Bristol; but I shall take the Bang back with me to Gunville, as Wedgwood will assuredly be there in the course of ten days. Jos. Wedgwood is named the Sheriff of the County. When I have heard from Wedgwood, or when he has tried this Nepenthe, I will write to you. I have been here nearly a fortnight; and in better health than usual. Tranquillity, warm rooms, and a dear old friend, are specifics for my complaints. Poole is indeed a very, very good man. I like even his incorrigibility in small faults and deficiencies: it looks like a wise determination of Nature to let well alone; and is a consequence, a necessary one perhaps, of his immutability in his important good qualities. His journal, with his own comments, has proved not only entertaining but highly instructive to me.
I rejoice in Davy's progress. There are three Suns recorded in Scripture:—Joshua's, that stood still; Hezekiah's, that went backward; and David's, that went forth and hastened on his course, like a bridegroom from his chamber. May our friend's prove the latter! It is a melancholy thing to see a man, like the Sun in the close of the Lapland summer, meridional in his horizon; or like wheat in a rainy season, that shoots up well in the stalk, but does not kern. As I have hoped, and do hope, more proudly of Davy than of any other man; and as he has been endeared to me more than any other man, by the being a Thing of Hope to me (more, far more than myself to my own self in my most genial moments,)—so of course my disappointment would be proportionally severe. It were falsehood, if I said that I think his present situation most calculated, of all others, to foster either his genius, or the clearness and incorruptness of his opinions and moral feelings. I see two Serpents at the cradle of his genius, Dissipation with a perpetual increase of acquaintances, and the constant presence of Inferiors and Devotees, with that too great facility of attaining admiration, which degrades Ambition into Vanity—but the Hercules will strangle both the reptile monsters. I have thought it possible to exert talents with perseverance, and to attain true greatness wholly pure, even from the impulses of ambition; but on this subject Davy and I always differed.