" E l e k t r a " Dry Fire Extinguisher for Electric Installations. R. NAGEL. (Elektrotechnik und M~schinenbau, xxix, 58I.)--This is the Elektra Trockenfeuerl6scher made by H. Kfinzel, of KSlnLindenthal. The tests were made in the Cologne municipal electricity works. The apparatus is a slightly conical tube, 75o mm. long, charged with a white p.owder which liberates carbon dioxide when heated; the tube consists of an insulating material, 2 mm. thick. The powder stood 5o,ooo volts alternating for five minutes when forming a bridge between termir~als of the horn type. Arcs were extinguished by throwing the powder on them, and a fire built of wood soaked in petroleum, sending up flames close to two vertical bus-bars under I2,OOO volts alternating, was extinguished without danger to the operators and without causing strong current fluctuations. Battery T r u c k - c r a n e s for Handling Freight. ANON. (Eng. Record, lxiv, 6o.)--Each truck is an electric vehicle with a swinging crane mounted on the front end. The hook of the crane is raised and lowered by a 1-ton hoist mounted at the back of the crane; the motors driving the hoist and the vehicle are operated from a battery at the rear end of the vehicles. If the parcel is not to be moved over IO feet vertically it can be deposited within a 6 foot to 8 foot radius, the vehicle remaining stationary; or the parcel may be lifted and the vehicle moved to the point of deposit. The vehicle has a short wheel-base and can exert a draw-bar pull of 2,ooo pounds. A Silica Standard of Length. G. W. C. KAYE. (Roy. Soc. Proc., Set. A, Ixxxv, p. 43o.)--In making primary standards of length objections are made to (I) copper alloys, (2) platinum, (3) iridio-platinum, (4) nickel, and (5) invar for various reasons. Fused silica has a remarkable combination of good qualities: (a) very small thermal expansion, (b) very small thermal hysteresis, (c) cheapness, (d) low density; while its weak points, v/z., (a) frangibility, (b) comparatively low elasticity, and (c) slight solubility in water, can be treated as negligible when used only by skilled operators, as is the case with primary standards. The present metre standard, the first of its kind, consists of a tube of silica with horizontal slabs of the same material fused into its ends. These slabs are optically worked, plane and parallel. The under sides are platinized, and the defining lines of the standard are made by ruling through the platinum film with a diamond. The standard is supported at the Airy points. Care is taken to allow for viewing the defining lines through the slabs, also for viewing through water or other liquids. The standard was annealed by slowly raising it to 45o ° C., maintaining it at that temperature for eight days, and slowly cooling it during fourteen days. Annealing caused a shrinkage of about one-half a micron.