TECHNOLOGICAL REPOSITORY; OR, DISCOVERIES AND IMPROVEMENTS IN THE Useful Arts, BEING A CONTINUATION OF HIS TECHNICAL REPOSITORY. BY THOMAS GILL, Patent-Agent, AND DEMONSTRATOR IN TECHNOLOGY, ON THE APPLICATION OF UPWARDS OF TWENTY YEARS A CHAIRMAN OF THE COMMITTEE OF MECHANICS IN THE AND COMMERCE, ADELPHI, LONDON ; HONORARY MEMBER OF THE ROYAL PRUSSIAN ECONOMICAL SOCIETY OF POTSDAM; AND VOL. I. LONDON: PRINTED BY T. AND J. B. FLINDELL, 67, ST. MARTIN'S-LANE; EDITED AT GILL'S PATENT AGENCY & COMMISSION OFFICE, PUBLISHED BY THOMAS HURST, EDWARD CHANCE, AND COMPANY, AND SOLD BY ALL PRINCIPAL BOOKSELLERS AND NEWSMEN IN TOWN AND COUNTRY. - 1827. GILL'S TECHNOLOGICAL REPOSITORY. I.—On splitting, cutting, and polishing Diamonds; and on forming, mounting, and using Engravers, Glaziers, and Writing Diamonds, Diamond Dust, &c. By Mr. EDMUND TURRELL, Engraver. WITH A PLATE. DEAR SIR, 46, Clarendon-street, Somers-town, June 10, 1827. I MENTIONED to you, several years since, my intention of giving you for insertion in your.valuable work, an article on the above interesting subjects; being chiefly the substance of memorandums I had taken some years ago, when I was afforded a favourable opportunity of witnessing the actual performance of several of the processes, by some Jews, who follow the profession of diamond cutting. I had, however, as I then informed you, lent those memorandums to Bryan Donkin, Esq., the celebrated engineer; and he, on his removal from his former residence to his present one, in the hurry and confusion incidental to such removal, having mislaid them, it was only lately that he happened to find and restore them to me. I have, at the request of several respectable members of the Royal Institution, had the honour of reading this article on one of the Friday evening conversationes, held in that valuable institution; and I likewise more recently repeated it, at the meeting of the Society of Civil Engineers; and the high and marked approbation it received in both instances, convinces me that it contains much useful information on these interesting subjects, which is well worthy of being more widely diffused, through the medium of your Repository. VOL. I. B I now, therefore, present to your, and your readers, notice, a few observations upon the application of the diamond and other precious stones, to some of the arts and manufactures, that are successively practised in this country. I must, however, previously intreat your indulgence to those imperfections, which must necessarily attend any endeavour on my part to describe the details of subjects, which I do not profess to practise. If many of the arts that are practised in this country could be readily seen and investigated by the public, there would be no occasion for my directing your attention to the subjects I am about to offer to your notice; but, as many really meritorious individuals are for years together employed in their lonely attics upon the most ingenious pursuits, and entirely unknown to any but their constant employers, so it must necessarily follow, that their modes of operating, and all the curious technicalities of their various arts, are hidden from the public, and knownonly to those professing, or connected with their arts. The Rev. Dr. William Pearson, F. R. S., in one of his articles in "Rees's Encyclopedia," states, that "if you would investigate the means by which the beautiful specimens of clock and watch-work are produced in this country; you must consent to enter the most obscure courts, and alleys, where, having mounted to the attic regions, you will there find the illiterate inmates ing eniously pursuing their daily avocations, unknown to the public, and often completely unacquainted with the scientific principles that are so intimately connected with their pursuits." I however trust, that the efforts which have already been made, and are still making, to diffuse and inculcate scientific information, amongst the class of persons I have just alluded to, will soon have the effect of removing such a stigma, and render such remarks obsolete. These circumstances, therefore, have induced me to offer to your notice a few facts relative to the methods |