It consists of a short tube of metal inserted into a hole near the top of a longer tube, and soldered in that position. The short tube, is lined with a composition made by mixing together two parts of chlorate of potassa and one of sulphurate of antimony, moistened with gum water. A serrated wire passes through the short tube and a hole opposite to it in the side of the long one, the open end of the short tube being compressed with nippers, and the wire at the end of the serrated part doubled under to prevent any displacement. The other end of the wire is doubled and twisted by machinery. The long tube is filled with musket powder, its upper end being closed with shellac-varnish, and its lower with shoemakers-wax. [Sidenote: 116]] 24. What advantage does the friction tube possess? It gives an enemy at night no clue to the position of your piece, as does the lighted port-fire, or slow-match. 25. What is _slow-match_? A slow burning match prepared from hemp or flax slightly twisted, soaked in a strong lye, or in water holding in solution sugar of lead. Cotton rope well twisted, forms a good match without any preparation. 26. How long does slow-match prepared from hemp or flax burn? Four to five inches to the hour. 27. What is the use of slow-match? It is used principally for the purpose of retaining fire in the shape of a hard-pointed coal, to be used in firing cannon, fire-works, &c. It was formerly used in field batteries for lighting the port fires with which the pieces were discharged; but both are now entirely superseded by the friction tube. 28. What is quick-match? It is a match made of threads of cotton, or cotton wick, steeped in gummed brandy or whisky, then soaked in a paste of mealed powder and gummed spirits, and afterwards strewed over with mealed powder. 29. How long does it burn? One yard burns in the open air thirteen seconds. 30. What is the use of quick-match? To fire stone and heavy mortars, and sometimes in proving pieces. It is extensively used in priming all kinds of fire-works, such as fire and light balls, carcasses, rockets, priming-tubes, &c., and in conveying fire very rapidly from one portion of a piece of fire-work to another. [Sidenote: 117]] 31. When used for discharging cannon, how is the quick-match set fire to? By a slow match, port-fire, or any other convenient material. 32. When used to prime carcases, &c., how is it set on fire? By the flame from the piece. 33. What is _Valenciennes_ composition? A compound of 50 parts of nitre, 28 of sulphur, 18 of antimony, and 6 of rosin. 34. What is its use? As an incendiary composition, in charging shells for the purpose of increasing their destructive property, by setting fire to buildings, shipping, &c. [Sidenote: 118]] PART XI. PLATFORMS. 1. What is a _platform_? A strong flooring upon which a piece of ordnance, mounted on its carriage, is manœuvred when in battery. 2. What is the object of a platform?