Crystal Palace International Electric Exhibition 1881-82

77 277 .—T. Crampton & Co., 251, High Holborn, W.C. Electric Clocks, &c. Southern Gallery. 278 .—John Davis & Son., All Saints* Works, Derby; London Office, 118, Newgate Street. Davis’s Improved Hedley Dials. This dial combines all the latest improvements of the best Hedley, with, the outside vernier of the theodolite. The improve- ment consists of an arrangement by -which the bearings are taken simultaneously with loose needle and vernier, the latter automati- cally checking the former, thus any error arising from incorrect reading or from any local attraction is detected. Biram’s Patent Anemometers to ascertain the ventilation in mines and sewers and the draft of furnaces. Concert-Room Gallery. 279 .—Joseph Davis & Co., Fitzroy Works, Kennington Park Road. Compasses, Barometers, and Meteorological Instruments. Eastern Gallery. 280 .—E. Dent & Co., 61, Strand. Electrical Clocks governed from the Great Exhibition Clock; non-Magnetisable Watches, specially designed for use of telegraphic and electrical engineers; Small Portable Galvanic Chronograph, constructed for the Govern- ment ; Electrical Relay for 3 currents, as constructed for the Royal Observatory, Greenwich; Mariners’ Compasses as used in the British Navy and by the Royal National Lifeboat Institution. Western Gallery and various parts of the Building. 281 .—F. E. Fahrig, Electrician, Southampton. Selt-acting Regulators, Dials, and Electric Clocks in general. Southern Gallery. 282 .—J. Faulkner, 13, Great Ducie Street, Strangeways, Man- chester. Diagrams illustrating the great waste of power in electro magnets as heretofore made, and the economy of altandæ electro magnets. In electro magnets, as usually made, only the mag- netism in the centre o£ the coils of wire is used and the external rays entirely discarded. These diagrams are produced by scattering iron filings upon papers prepared with paraffin, placed over ordinary electro magnets and altandæ electro magnets respectively,, and they show that round (see c, df half round, and flat covers of iron (see k, I, m, n, o') may be used, and thereby the force so shaped and concentrated as to meet any form or position required.. —John Faulkner, Manchester. Diagrams taken from : (a) End of coil, without any iron core ; (&) End of coil, containing an iron core ; (c) End of coil, with an iron core and thin iron outer cover; (cZ) End of coil, with an iron core and thick cover; (e) End of coil, with a hollow iron core, a thin iron cover, and an iron washer let in the end; (/) Length of coil, with an iron core; (ø) Length of coil, with an iron core and thick iron cover; (7i) Length of coil, with an iron core, three sides covered and one side open; (i) Length, of coil, with, an iron core, three sides covered, one side open, and an armature at one end; (/) Length of coil, with an iron core, three sides covered, one side open, with two armatures, one on each end; (7c) End of coil, with one iron flat side; (f) End of