The daily morning Alaskan., 1900-01-25

The "Erosive Action of Innamed
 Gases" Causes the First Serious In-
 jsry-Hsw the Projestile Helps to
 Kin the Gun.
 The larger a cannon the more exten' sive are the injuries it receives with each successive discharge All damage done to a gun is internal The separate action of the powder and the projectile damages the piece every time it Is aimed and fired Obviously the amount of the damage depends upon the material and workmanship of the gun. Men who make big guns describe the harm done their pets with many intricate and puz. zling terms of a scientific turn. In one case a gun is damaged because the part of the bore whicl contains the powder is enlarged. This happens when the metal is compressed. and 1t ismore dan eerous and moro plainly seen if the gunners have been using wads between their explosive and their projectile.
 Then. again. cavities are produced by the melting away of part of the metal by tho heat of combustion of tho charge. Cracks come from the tearing asunder of the particles of tho metal at the sur face of the bore When it is first made, a crack of this particular kind is barely perceptible. but S increases each time the gun is fired. Gradually it extends completely through the side of the piece The crack usually begins at the junction of the chamber with the bore, simply because, as guns now are, this part is not so well supported as the others
 Edward S. Farrow, U. s. A, is au thority on damage to guns, although, like all others who have studied the question, he does not agree with very many authorities on all the points to consider in the life of a cannon. He con- tends that throwing or scoring produced by tho erosive action of inhamed gases is the great disease which attacks the yety big guns first This particular in. jury is most apparent where the current of the gas is most rapid or at the inte- rior orifce of the vent and on the sur. face of the bore. directly over the seat of the projectile. This scoring begins very early in the life of a very large gun. but it is conceded that 1t does not become very important until the piece has been discharged considerably. Lieu tenant Farrow describes this scoring as resembling the bark of an aged elm tree. the metal being eaten away into irregu- lar furrows and ridges In extreme cases, however. scoring has not killed the gun, although in some cases it has acted like a wedge and split the bore at the place attacked.
 Where the action of the projeotile has ruined the gun the damage has been done around the projectile and in front of it The elasticity of the metal and the erowding up of portions of 1t in front of the shot cause a rebounding process The projectile, carried forward by tho force of the charge, strikes against the upper part of the bore; then it Is sent against the bottom and again bounds to the top, and SO on until it emerges from the piece The effect of this bounding motion is Co raise and de- press the gun tn it's trunnion holes. The accuracy of fire is diminished, and, of course, the gun Is unfit for service Bronze guns arc the worst sufferers in this way. Mortars-short and dumpy- are not affected.
 To stop the bounding of the projectile gunners wrap the shell in cloth or pa pea or else shift the base of the mass Co be hurled. This last process is con sdered the best and is done by reduc. ing the diameter of the cartridge and adding to it's length. Projectile injury IS also caused by furrows or scratches made by rough shells or case shot Small fragments. too break away very often from the shells and give the bore q grinding and cutting process, produo. tive of great damage.
 Enlargement of the muzzle is another serious injury produced by the proJec' tile This is caused by process which seems unavoidable. As the shell leaves the piece it strikes against one portion of the bore. The resistance at the mouth being less than at any other point, tho metal naturally yields, and tho muzzlo of the cannon is elongated in vertical direction.
 Some men who ought to know say that l5O shots is the life of a very big gun-a l2 or IS inch weapon. Others place the number of shots at 100 or 500 As a matter of fact. it is all guesswork The great Krupp gun shown at the Worlds fair and conceded to be perfect
 or supposed to be sO-has been dis charged less than ten times, and 1t Is now believed to have reached its limit On the other hand, the big guns of the American battleships have passed the time allotted theri by wise men who know guns and apparently are as good as when tested. How soon they may yield. however. is not in the books
 Lieutenant Farrow says that very largo gun should not be expected to stand more than 400 or 500 shots before it will be necessary 10 open a new vent closing the old one at its interior orifce
 When the gun dies-bursts-the lines of fracture are photographed. speci' mems of the metal are saved Tests are made and conclusions drawn. And Un' cle Sam has figured out SO many things in this same connection that his guns nowadays are conceded to be better than those of any other maker. They live longer than the wise ones say they should. Chicago Times. Herald.