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
SCIENCE TO THE USEFUL ARTS AND MANUFACTURES;

UPWARDS OF TWENTY YEARS A CHAIRMAN OF THE COMMITTEE OF MECHANICS IN THE
SOCIETY FOR THE ENCOURAGEMENT OF ARTS, MANUFACTURES,

AND COMMERCE, ADELPHI, LONDON;

HONORARY MEMBER OF THE ROYAL PRUSSIAN ECONOMICAL SOCIETY OF POTSDAM; AND
CORRESPONDING MEMBER OF THE ROYAL BAVARIAN POLYTECHNICAL
AND AGRICULTURAL SOCIETIES OF MUNICH.

VOL. II.

LONDON:

PRINTED BY W. SPIERS,

399, OXFORD-STREET;

EDITED AT GILL'S PATENT AGENCY & COMMISSION OFFICE,
125, STRAND, OPPOSITE EXETER 'CHANGE;

PUBLISHED BY THOMAS HURST, EDWARD CHANCE, AND COMPANY,
65, ST. PAUL'S CHURCH-YARD;

AND SOLD BY ALL PRINCIPAL BOOKSELLERS AND NEWSMEN IN TOWN AND COUNTRY,

1828.

GILL'S

TECHNOLOGICAL REPOSITORY.

I. On the French Manufacture of Enamelled Watch Dials*.

THESE are formed of thin plates of copper, on both sides of which the enamel is applied, and afterwards the hours, minutes, &c., are painted upon them, also in enamel. The following is the process employed. After having prepared a thin plate of copper, of a convenient size, they form it to shape with a hammer, the face of which is slightly rounded, supporting it at the same time upon a block of wood made a little concave upon its surface; the plate is thus easily made into form. A hole is made in its centre, which is afterwards enlarged with a round taper broach, to the size of the hole in the watch-plate; but we must take care to insert the broach on the concave side of the dial, in order that it may form a bur, or border around the hole above, which serves to retain the enamel in its place. We place the dial upon the watch-plate, and pass the broach through the holes in them both at once, in order to form the hole at right-angles with the plate, holding it firm with plyers; and we likewise pierce through the dial the holes for the studs, which holes are also previously formed in the watch-plate; we likewise make the hole for the watch-key to enter; and we form a border around this hole in a similar manner to that around the central hole, and for the same purpose, of retaining the enamel around the hole.

We next fit on the feet or studs of the dial: in order to

* From the Dictionnaire Tecknologique.