GUN-BOAT. 



GUN-COTTON. 



Holland, and in Or. Ure's ' Dictionary of Art*.' Until a comparatively 

 recent period all military guns, and most of those used for sporting 

 purppMs. were made with flint-locks, in which the ignition of the 

 priming-powder was effected by the midden (troke of a wedge-ahaped 

 flint against a piece of ateel, by which a alream of sparks waa directed 

 into the pan containing the priming ; and the greater number of flints 

 required for this un caused the cutting, or rather breaking, of them 

 to be a considerable branch of industry. When the first attempt 

 was nude to substitute for thin contrivance the use of a fulminating 

 or detonating powder, which, being ignited by simple percumion, 

 should set fire to the ordinary gunpowder in the touch-hole, we are 

 not aware ; but, according to the work nut referred to, the first per- 

 cussion-lock was invented by the Rev. Mr. Forsyth, of Belhelvie, in 

 Scotland. The improvement has, however, led to alterations in the 

 oonstructiun of gun-locks which, OR Holland observes, are hardly infe- 

 rior to that which took place on the suKttitution of the modern flint 

 for the ancient fire-match. The pan which contained the priming- 

 powder, and the cover which shielded it until the moment of preirii> 

 to^fire, are rendered unnecessary, their place being supplied by a small 

 upright nipple, the perforation of which coincides with, and forms a 

 continuation of, the touch-hole of the barrel. The cock, or striking 

 part of the lock, instead of carrying a clamp to hold the flint, becomes 

 a simple hammer, with a snout adapted to fall exactly upon the top of 

 the nipple. The fulminating substance is usually placed, for conve- 

 nience, in a small copper capsule or cap, resembling a thimble in shape, 

 which fits on to the nipple, and, if not blown to pieces by the explo- 

 sion, is removed previous to reloading. The hammer is provided with 

 a shield to prevent any fragments of the copper cap from flying against 

 the face of the shooter. The great superiority of the percussion prin- 

 ciple in safety and certainty of action led to its adoption, after expe- 

 riments most decisive as to its superiority, especially in wet weather, 

 over the flint-lock, both in the arms of the British and all Continental 

 armies. A long article relating to the compounding and use of 

 percussion-powders made with fulminate of mercury, which forma the 

 base of most such compositions, is given under " Fulminates," in Dr. 

 Ure's ' Dictionary of Arts.' 



Rifled guns are described under RIFI.E. 



(Greener, The Gun, and Treatite on (iunnery ; Holland, Manufactures 

 in Metal, in Lardner's ' Cabinet Cyclopaedia,' vol. ii., pp. 94-123 ; 

 Barlow, Treatite on Machinery and Manvfaclu.ro, in the ' Encyclopaedia 

 Metropolitana ; ' Dodd, Jirititk Manufacture* Metals, in Knight's 

 'Weekly Volume,' pp. 102-107; Dr. Ure, Dictionary of Arts, Manu- 

 facture!, and Mining; Babbage, Economy of Machinery and Manu- 

 facture*, sec. 862, 363.) 



GUN-BOAT. This term has for many years been applied to small 

 craft, mounting usually a single gun, when employed in the defence of 

 coasta ; and until very recently it indicated vessels of no peculiarity of 

 construction, strength having been considered the main qualification, 

 such as sufficient to sustain the continued working of a gun of light 

 calibre. 



Change in naval tactics has, however, from improvements in pro- 

 jectiles, made such progress, that a totally new class of vessels has 

 been called for. They are still further in request from the facilities 

 afforded by progress in the art of propulsion. For a long period the 

 collecting of a large number of guns in one ship had been thought the 

 perfection of a floating battery ; but the experience of the last Russian 

 war established the importance of having a part of the armament of a 

 fleet detached in small vessels, calculated from their light draught of 

 water to navigate estuaries and parts of the coast which had hitherto 

 been protected by their shallows. 



Nor is it to this alone that the gun-boats of the present day owe 

 their origin. The use of steam has so changed the features of naval 

 warfare, that henceforward they will resemble more and more the evo- 

 lutions of an army in the field ; and, above all qualifications, ) 

 iii ni'in-i iirroi'i must be paramount ; and such is not so easily attained 

 in larj-ie, long, heavily-armed ships, which, whatever may be the weight 

 of metal thrown by their broadsides, cannot be turned to an opposite 

 direction except within a considerable area of space and without the 

 lapse of several minutes. Hence the attention of government has been 

 directed to the building of the modern "gun-boat. 



The ease with which a small vessel of about 100 feet length and 

 22 feet beam, having a light draught of about 64 feet at the load 

 water-line, could be manoeuvred under the agency of steam as applied 

 to the screw, even when armed with a heavy pivot-gun equal to the 

 largest used on board the longest three-decker, was at once apparent to 

 the Admiralty ; and, accordingly, about 160 had been constructed by the 

 beginning of 1860, 88 of them being actually on foreign service, some 

 in the remotest parts of the globe ; and before many months the num- 

 ber will in all exceed 300. These are generally armed with one 

 68-pounder gun of 95 cwt., so fitted as to be used either a-head or 

 a-stern, or in any direction ; while the vessel may be turned round 

 almost in her own length, and in the lapse of a few seconds only. 

 Some gun-boats have, in addition, a 32-pounder ; others have two or 

 four braa* howiUers, 24-pounders. These vessels are propelled by 

 high-preawire engines of 20, 40, or 60 horse-power. In these gun-boats, 

 specially constructed for the purpose, and the crews of which are pro- 

 tected by shifting iron screen-plates from the effect of rifles, we possess 

 a flotilla of formidable character; and as in any future naval contest 



these little vessels are destined evidently to pUy a conspicuous part, 

 especially when armed with Armstrong's guns, we give a sketch as 

 under. To prevent accident* from fouling the screw when dismasted, 



and also to prevent all avoidable encumbrance upon deck from the 

 same cause, when in action, gun-boata are lightly rigged, have three 

 short masts, and are fitted with gaff-sail*. 



A class of what may be called " despatch gun-boats," or, aa they are 

 officially called, " screw steam gun-vessels," and at present consisting of 

 about 10 in number, are of larger dimensions, being, as the 

 would imply, built with capabilities for speed. They are nearly 

 200 feet long, and have about 30 feet beam, drawing upwards of 11 feet 

 water, are of about 450 tons, and propelled by engines of 40, 0, and 



160 horse-power. Some carry a single gun of 95 cwt., others two or 

 four 24-pounder 12 J cwt. brass howitzers, in addition ; they are rigged 

 aa three-masted two-topsail schooners. Several others, on improved 

 principles, are now in course of building. 



(Sir Howard Douglas, On If aval Tactics; Screw Fleet of the Nary, by 

 Capt. E. P. Halsted, R.N.) 



GUN-COTTON. Pyroxylin. If finely carded cotton be soaked for 

 a short time in very strong nitric acid, and then washed and dri<-il. it 

 will be found to have acquired such powerfully explosive properties as 

 to render it capable of being substituted for gunpowder. The cotton 

 is not altered in appearance by this process, but its weight is increased 

 to almost double. The reason of this increase in weight is that the 

 elements of nitric acid (NO S ) replace, in the cotton, the elements of 

 water (HO), the equivalent of nitric acid and of water being, as 

 known, six to one ; the increased weight is thus readily accounted for. 

 The increase in weight, however, is not constant, but differs in an exact 

 ratio with the strength of the nitric acid employed ; the explosive and 

 other properties of the resulting gun-cottons also differ considerably. 

 In this way three, if not more, compounds may be prepared, in the 

 first of which three equivalents of water, in the second four, and in the 

 third jive equivalents of water are respectively replaced by three, four, 

 and five equivalents of nitric acid : or what is almost the same thing, 

 only theoretically more correct, three, four, and five equivalents of 

 hydrogen are replaced by equal numbers of equivalents of hyponitric 

 acid (NO,), the displaced hydrogen combining with the remaining 

 equivalents of oxygen from the nitric acid. 



Finely carded cotton has already been shown to be nearly pure 

 cellulose [CELLULOSE], and, as the other varieties of cellulose are 

 similarly acted upon by nitric acid, these explosive bodies may be 

 viewed as nitro-substitution compounds of cellulose, and the three 

 gun-cottons thus represented : 



Cclluloic 

 No. 1. TrinitrocclluIoM . 



No. 2. Tctranitrooellulosc . 

 No. 3. PcntanitroceUuloM 



C..U..O,. 



c,. 



HI. 



(NO,),, 



,2HO 



No. 8 is very explosive, burning so rapidly when ignited, that the 

 experiment may be performed on the palm of the hand without n 

 sensible amount of heat being communicated to the flesh, or on a heap 

 of gunpowder without danger of the latter being set fire to. Thi* 

 variety of gun-cotton is best prepared by digesting one part of cotton 

 in fifteen parts of a mixture of equal volumes of nitric acid of sp. gr. 

 1 ."<">, and of sulphuric acid of sp. gr. 1*845. The cotton must be 

 completely immersed for about four or five minutes, and then plunged 

 into a large quantity of cold water and washed till all trace of arid is 

 removed: it is finally dried over a water-bath. So prepared, gun- 

 cotton possesses an explosive power equal to three times its weight of 

 gunpowder. Gun-cotton, however, has not superseded the use of gun- 

 powder for several reasons, the most fatal one being iu liability to 

 spontaneous ignition. From the greater rapidity of inflame 

 gun-cotton also produces greater strain upon the gun, and hence 



