112 ANNUAL OF SCIENTIFIC DISCOVERY. 



endurance of any gun is thus to be ascertained, the regular 

 powder-charges, or any le??s quantity deemed desirable, may be 

 used, the enlargements being recorded after each discharge. A 

 9-i)ounder bore gun made ot my metal but reduced 12 inches in 

 diameter has been so tested, and has had 18 full charges of li lbs. 

 lired from it. The expansion in the bore is now .1903 inches, and 

 that of the outside diameter is .0-18i> inches. — Van Nodrand's Eng. 

 Mag. 



VELOCITY OF CANNON BALLS. 



At the late ordnance experiments at Fortress Monroe, the initial 

 velocity of cannon balls was tested by a very delicate instrument, 

 •' the Schultz Chromoscope." The apparatus, which is operated 

 by electricity, is thus described: two wire targets are placed, one 

 about 20 yards from the gun, and the second about the same 

 distance further on. These are connected by a tine insulated wire 

 with the instrument, which is about 400 yards in the rear of the 

 ordnance. The instrument is adjusted on a plan similar to an 

 electro-balistic machine. When the shot is fired, it cuts the wire 

 in the first target, and then that of the second, — the instant each 

 wire is severed being recorded by the instrument. The interval 

 of time occupied by the ball in passing from one target to the 

 other furnishes the data for obtaining the initial velocity of the 

 shot. 



SYSTEM OF MONCRIEFF. 



It consists of three parts: 1st. The mechanical principle of the 

 gun-carriages. 2d. The form, internal and external, of the bat- 

 teries. 3d. The selection of ground for placing the batteries, and 

 the arrangement for working to the greatest eflect ; or, in other 

 words, the tactics of <lefence for positions where the system is 

 employed. The principle on which the carriage is constructed is 

 the first and most important part of tiie new system, because on 

 it depends the possibility of api)lving the other parts. This prin- 

 ciple may be shortly stated as th:U: of utilizing the force of the 

 recoil in order to lowei the whole gun below the level of the crest 

 of the parapet, so that it can be loaded out of sight and out of 

 exposure, while retaining enough of the force above referred to 

 to bring the gun up again into the firingor fighting position. This . 

 principle belongs to all the carriages ; but the forms of these car- 

 riages, as well as the method in which this principle is a})plied, 

 vary in each case. For instance, in siege guns, where weight is 

 an clement of importance, the recoil is not met i)y counterpoise. 

 With heavy garrison guns, on the other hand, which when once 

 mounted remain permanent in their positions, there is no objection 

 to weight. In that case, therefore, the force of gravity' is used to 

 stop the recoil, because it is a force always the same, easily man- 

 aged, and not likely to go wrong; and as these carriages are em- 

 ployed for the most powerful guns, it is a great advantage to have 

 the most simple means of working them. It has been already 



