92 ANNUAL OF SCIENTIFIC DISCOVERY. 



on a ship's deck may be used both as a cannon and a mortar, and that 

 a ship which carries forty guns may be said to carry forty guns and 

 forty mortars. 



Trial of the great "Rodman" Gun. The great 12-inch rifled 

 cannon, constructed according to the plan devised by Lieut. Rod- 

 man, U. S. A. (see Annual Sri. Dis. 1861, p. 50), for the govern- 

 ment, has been mounted during the past summer at Fortress Alon- 

 roe, and thoroughly tested. This gun is sixteen feet long, weighs 

 fifty-two thousand pounds, and carries a solid shot weighing four hun- 

 dred and twenty-three pounds. The N. Y. Tribune gives the fol- 

 lowing spirited description of the firing of this monstrous piece of 

 ordnance : 



" First, the swab, which two men insert, cleans the interior ; then 

 comes a man with a red flannel bag filled with powder on his shoul- 

 der; it is the cartridge; and the ramrod, worked by four men, sends 

 it home. Then conies the process of getting the shot to its place, 

 a mass of metal that four men carry with difficulty. It is first 

 rolled into an iron cradle or wide strap, looped with a rope, through 

 which a piece of strong wood, several feet long, is inserted. Thus 

 slung, the men tug the shot up the steps of the platform, some ten 

 feet high, to the mouth of the gun. Another lift brings it on a level, 

 and it is slid into the muzzle and pushed to its place. The gun 

 is then elevated by means of an iron bar, the gun being nicely bal- 

 anced on its trunnions. The priming wire performs its office, the fuse 

 is inserted, and the lanyard is attached. ' Ready,' says the sergeant ; 

 ' Ready fire ! ' says the lieutenant. A terrific crash, a sheet of flame, 

 and the trembling of the earth, follow. At the same time there is a 

 screech and a scream caused by the shot, a black mass which you can 

 see, in its flight, yelling like an infuriated devil let loose from the 

 infernal regions." 



The results of the practice with this gun demonstrate its complete 

 success, and it is probable that government will order their construc- 

 tion in considerable numbers for our sea-coast fortifications. In its 

 ranges for shot and shell, it does not exhibit any decided advantages 

 over those obtained from the 10-inch gun, up to 10 elevation; but 

 beyond this elevation the gain is considerable, and may be estimated 

 at 'about GOO yards for the elevation of 28 35'. With 39 elevation, 

 and a charge of forty pounds large-grained powder, it is probable a 

 range considerably beyond four miles might be attained. . Indeed, the 

 conviction appeared to be general among the officers who witnessed 

 the firings, that the gun could, if necessary, bear much heavier 

 charges, though, for all ordinary uses, it is doubtless best to keep them 

 down to somewhat less than the above. 



The Chronoscope. This name has been given to a recent English 

 invention, which is intended to measure accurately the time of the 

 flight of projectiles. It consists, in the first place, of a barrel, revolv- 

 ing by clockwork, which is cased with paper, upon which four or more 

 pencils trace a continuous line. These pencils are in communication 

 with a voltaic battery and electro-magnetic apparatus, and the tar- 

 gets, made of fine crossed wire, which may be four or more in num- 

 ber, according to the pencils, are placed 200, 300, 500 or 700 yards 

 apart. When the shot strikes the first target, the current is broken 



