100 ANNUAL OF SCIENTIFIC DISCOVERY. 



since, and which were made by Mohammed II., and asked whether bronze 

 might not now be used instead of cast-iron. He suggested the probability 

 that on experiment railway-iron might be found better than cast-iron for ord- 

 nance. Mr. Fairbairn said the material of which guns were made was not 

 so good as it was fifty years ago. He was present at "Woolwich and saw the 

 practice of the guns there. One of them seemed properly molded in every 

 part ; but it was found that the welding in one part was not sound, and the 

 gas getting into the fracture operated just like a wedge, and split it as if it 

 had been made of paper. Another was formed of steel bars, with a breech of 

 cast-iron attached to it. The breech was entirely blown off the gun, and the 

 bars torn asunder. It appeared to him absolutely necessary to have such a 

 material as would not only resist the severe impulse which the discharge of 

 the shot caused, but be perfectly solid in the mass. If they were made of 

 parts, such as the staves of a cask, these opened, and the result was the frac- 

 ture of the gun. The Stirling gun was a mixture of wrought with cast-iron, , 

 and it certainly carried one fourth or one fifth more of common pressure, but 

 when applied to artillery under Colonel Dundas, after a few rounds the pieces 

 were burst. The mode of casting these large guns is also defective. They 

 were generally cast solid, and in the cooling the metal was left exceedingly 

 porous in the center, and when one began to bore out the gun, one found it 

 was not of so close a texture inside as out. Now they took the precaution of 

 having cores in the middle, through which they sent a current of cold water 

 to cool the inside simultaneously. Dr. Robinson : About a century ago they 

 cast them hollow, and it was thought a great improvement to cast them solid. 

 Mr. Fairbairn believed if they went about the work more carefully, they 

 would arrive at a safer and better mode of casting than at present. If the 

 mortars were made a foot longer, he believed, instead of sixty pounds, fifty 

 pounds of powder would carry a shell of the same weight, and to a greater 

 distance, and with greater accuracy. He thought, in the mortars, a great 

 quantity of the metal was in the wrong place hi a great many cases. They 

 had the same thickness of metal at the mouth as at the breech, whereas it 

 might taper without any danger, the pressure being less at the mouth. He 

 explained an ingenious bah 1 , in which there was a spiral tube, so that the 

 bah 1 with an ordinary gun suited all the purposes of a rifle ; but he did not 

 know whether the experiment was successful or not. Till lately guns of the 

 ordinary caliber would stand six hundred or seven hundred rounds before they 

 were injured, but they always gave way at the vent. But they got into a 

 plan of putting a tube into the vent, which made them stand six hundred or 

 seven hundred rounds more. Now-a-days the same guns would not stand 

 one hundred rounds ; perhaps the reason was that the metal was not properly 

 selected. The iron procured by hot blast is excellent for machinery purposes ; 

 but he did not think it the best for artillery. With regard to the Turkish 

 artillery, he was at Constantinople some years ago, and they are almost all 

 made of a mixture of brass and tin. Mr. Mare, at Blackwall, is now con- 

 structing a gun three feet in diameter the breech of cast-iron and the tube 

 of direction of wrought-iron. Whether it would answer or not he did not 

 know. Dr. Robinson : The bronsw guns failed in a very remarkable manner. 



