50 ANNUAL OF SCIENTIFIC DISCOVERY. 



Monster Gun. One of the largest cannon ever constructed has been cast 

 during the past year at the Fort Pitt Foundry, Pitsburg, under the super- 

 intendence of Lieut. Rodman, of the Ordnance Department. It was cast 

 hollow, upon a core, through which a stream of cold Avater was constantly 

 passing, at the rate of about forty gallons per minute : the object being to 

 produce metal of uniform texture, from the equal cooling and contraction of 

 the mass. The core-barrel, Avhich formed the bore of the gun, was removed 

 twenty-four hours after casting, and water, at the same rate as before, was 

 caused to circulate through the cavity, descending along a tube to the bottom 

 of the bore, rising up by another tube, and escaping through a wrought-ii'on 

 pipe, cast into the spruehead of the gun about fifteen inches from the casting. 

 The metal was entirely cold at the end of seven clays after casting, a 

 shorter time than is required for cooling an eight-inch solid-cast gun. The 

 bore of this gun is fifteen inches in diameter, and thirteen feet long in the cyl- 

 inder, which is terminated by an ellipsoidal chamber nine inches long, making 

 the total length of bore one hundred and sixty-five inches, or thirteen feet 

 nine inches long. The thickness of metal in the breech is twenty-five inches, 

 and the total exterior length is fifteen feet ten inches. The greatest exterior 

 diameter at the muzzle is 48.1 inches. The weight of the gun is 49,009 

 pounds. It is to carry a shell of three hundred and fifty pounds, and a solid 

 shot of four hundred and tw r enty-five pounds weight. 



In illustration of the advantage of the mode of casting adopted in this gun, 

 a specimen of cast iron, cut from a shaft cast in the usual way, was recently 

 exhibited at a meeting of the Franklin Institute, Philadelphia. In the middle 

 of the piece, where the iron had retained its heat and softness for the longest 

 time, the contraction of the surrounding parts had caused the metal to assume 

 an open, loose character, whilst the central portion was thrown into groups 

 of spiny formation, resembling frost-work. Experiments made with Rod- 

 man's gun at Old Point Comfort, Va., are reported as highly satisfactory. 



THE CONSTRUCTION OF ARTILLERY. 



The very interesting question of the best method of construction to be 

 adopted for artillery has recently been handled with unusual detail by a 

 body of gentlemen who, it may fairly be presumed, possess peculiar qualifi- 

 cations for forming an authoritative opinion on the point. On the fourteenth 

 of last February, Mr. Longridge, a civil engineer of considerable eminence, read 

 before the London Institution of Civil Engineers a paper on the subject; and 

 so great was the interest excited by his essay, that the discussion which fol- 

 lowed it was canned on for five consecutive evenings, being sustained by a 

 large number of the most distinguished authorities on the question, military 

 as well as civil. Although there was, as might have been expected, consid- 

 erable difference of opinion, often on points of no small importance, among 

 the gentlemen who took part in this lengthened debate, still, the complete 

 ventilation of this momentous question at the hands of such competent 

 authorities cannot but excite great interest. From a printed report of this 

 discussion we derive the following abstract: The one point to which Mr. 

 Longridge has directed his efforts is the construction of a gun which shall 

 be able perfectly to resist the utmost force of the explosive compound which 

 maybe used in it; in other words, the manufacture of a gun which gun- 

 powder cannot burst. In order to effect this, it becomes, in the first place, 

 necessary to ascertain, approximately, at least, the actual amount of the 



