NA TURE 



333 



THURSDAY, FEBRUARY 13, 1872 



THE " THUNDERER" EXPLOSION 



NOW that the Committee 'appointed to inquire into 

 the cause of the bursting of one of the 38-ton guns 

 on board the Thtniderer have made known the substance 

 of their report, it is no longer necessary to suspend judg- 

 ment and withhold comment for fear of prejudicing the 

 case. The abstract only of the report of the Committee, 

 ■which has reached us by telegram, states that the explo- 

 sion was due to a cause, -which, as far as we are aware, 

 was not anticipated by any one of the numerous writers 

 who have made suggestions or advanced theories on the 

 subject. They simply report that the gun having missed 

 fire when loaded with the battering charge, was again 

 loaded with a full charge, and fired with both of the 

 charges in the gun at the same time. We are bound to 

 assume that conclusive evidence of this extraordinary 

 occurrence has been obtained by the Committee, or the 

 statement would be simply incredible. Cases are re- 

 corded in volley-firing of a soldier loading charge after 

 charge into his musket or rifle in the days of muzzle- 

 loaders, being unaware that the first had missed fire until 

 the \'ioIent explosion, and perhaps bursting of his piece, or 

 the apparent growth of his ramrod showed that something 

 unusual was taking place, but that a squad of blue-jackets 

 serving a 38-ton gun should be unaware, or even uncertain, 

 if the 1 10 lb. of powder they were supposed to be firing had 

 exploded or not is beyond comprehension. Even if the 

 two guns in the fore turret were being fired simiUtaneously 

 by electricit)', the absence of recoil would have alone been 

 sufficient to indicate that the gun had missed fire. That 

 the rammer did not pass home might, it is conceivable, 

 have escaped notice in loading the second round with the 

 hydraulic gear, but we must look to the report of the 

 Committee for some explanation of the first miss-fire 

 having escaped notice. 



In the many suggestions that have been made re- 

 specting the probable cause of the disaster by the 

 writers of letters to the daily and weekly papers, it 

 appears to us that a too low estimate has generally 

 been made of the strength of the gun. It has been 

 assumed by many that if it could be shown that the 

 projectile slipped forward in the bore on the withdrawal of 

 the rammer, a sufficient cause for the accident had been 

 discovered. Experiments were at once tried at Woolwich 

 which established the fact that when no ring-wad was used 

 the shot frequently followed the rammer on its withdrawal 

 for a distance of three or four feet. Instances have also 

 been given of the bursting of fowling-pieces through an 

 accidental stoppage of the muzzle by snow or a wad, and 

 It was thought by many that a clear case had been made 

 out for the cause of the explosion. Sir William Palliser's 

 experiments, however, disprove the truth of this sugges- 

 tion, for, many years ago, in firing an experimental 8-inch 

 gun with various air spaces up to four feet between the 

 powder charge and the shot, he foimd that there was no 

 dangerous pressure in the bore. The gun made use of 

 in this experiment was an old cast-iron 68-pounder which 

 was converted into an 8-inch rifled gim, on Sir William 

 Palliser's system by the insertion of a coiled wrought- 

 iron tube 2 J inches thick. This g\m was fixed with 22 lbs. 

 Vol. XIX,— Ko. 485 



of powder and a shot of 180 lbs. weight, with successive 

 air spaces of 10 inches, 20 inches, up to 50 inches between 

 the powder and the shot, and sustained no damage. 

 Sufficient experiments have not yet been made to indicate 

 accurately all the variations of pressure that would be 

 introduced by an air-space between the powder charge 

 and shot, but the only cause which would tend to raise 

 the gas pressure, and in particular the longitudinal and 

 twisting strain on the gun, above that due to an ordinary 

 discharge is the fact that the pitch of the rifling would be 

 sharper where the projectile started in the former case 

 than in the latter. In the case of a fowling-piece the 

 cause of bursting with a slight stoppage at the muzzle is 

 probably due rather to the weakness of the barrel at that 

 part than to the excessive pressure. In the 38-ton gun, 

 with the heaviest charges employed on service, the central 

 part of the length of the g\m known as the i B coil is 

 probably amply strong enough to resist the pressure 

 brought to bear upon it, even if the shot was in this part 

 of the bore and the maximum gas-pressure exerted. Al- 

 though it has been shown by the report of the Committee 

 that none of the conjectures as to the cause of the 

 accident is correct, there is still utility in examin- 

 ing them, for, if valid, they might bring about a 

 similar accident at some future time, and should there- 

 fore be provided against. Though the nmning for- 

 ward of the shot when the gun is much depressed for 

 loading with the hydraulic gear would cause but a small 

 risk of explosion to the gun, it is so undesirable for many 

 other reasons, that means should be taken to render it 

 impossible, or at least render its detection a certainty. 

 The means at present employed to obviate the shifting of 

 the shot when once rammed home, consist of a ring wad 

 which fits round the pointed head of the shot, and is 

 firmly wedged in between it and the bore. Here again 

 we are provided with a very possible chance of an acci- 

 dent. The two letters of Sir William Palliser published 

 in the Times pointed out what appeared to us, before the 

 publication of the report, by far the most probable solu- 

 tion of the problem : it consisted simply in the employ- 

 ment at the same time of a gas-check and a ring-wad. 

 As clearly pointed out by Sir William, it is merely a 

 question of the relative coefficient of friction between the 

 shot and the wad and between the wad and the surface 

 of the bore, which has to decide whether the wad is 

 forced along the bore when the shot commences to move, 

 or whether the head of the shot is forced further into the 

 wad, wedging it tightly against the siurface of the bore. 

 This action would be impossible without the employment 

 at the same time of a gas-check, as the gas rushing past 

 the shot would inevitably dislodge the wad. The gas- 

 check consists of a cupped disk of copper with the peri- 

 phery turned down so as to form a flange ; this is fitted 

 to the base of the projectile, and, when fired, the pressiu-e 

 of the gas causes the flange to expand and press firmly 

 on the surface of the bore, both in the grooves and in the 

 lands between them, thus preventing the passage of the 

 gas past the shot. Sir William says : " With regard to 

 the friction between the wad and the gun, it is a fact that 

 when the atmosphere is moist the residue of the powder 

 deposits itself upon the surface of the bore in a blacky 

 greasy substance which reduces friction to a very low 

 point. On a dry day, however, this deposit assumes the 



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