206 REPORT — 1855. 



On the Machinery of the Universal Exhibition of Paris. 

 By W. Fairbairn, F.R.S. 



On the nmtual Influence of Capillary Attraction and Motion on Projectiles, 

 and its application to the coustrtiction of a neio kind of Rifle-shells, and 

 Balls to be thrown from common guns*. By James Gall, Jun., Editi- 

 burgh. 



The author pronounced tlie principle of rifling the shot instead of rifling the gun, 

 although inapplicable to small projectiles, to be absolutely necessary for large ones. 



1. The great difliculty arose from the envelope of condensed air which accompa- 

 nies every projectile. This is produced by three causes : — 1. The sudden pressure 

 and displacement of the air by the ball ; 2. Friction ; and 3. The attraction caused 

 by motion. The first may be diminished by having the projectile pointed like a ship's 

 bow. The second depends on the surface of the projectile. If it be rough and wet, 

 the friction is great ; if it be smooth and oily, the friction is small. This was illustrated 

 by the action of wind on water — oil on the water forms a vacuum between, and pre- 

 vents friction. The third depends on velocity. This was illustrated by inserting the 

 end of a quill into the centre of a card. When we blow through the quill against a 

 sheet of paper, the paper is attracted towards the card, instead of being blown away. 

 The stronger the blast the nearer it comes. 



2. He next showed how the projectile may receive a spiral motion after leaving the 

 gun, first by the action of the air on projecting blades in front, or lateral fins thrown 

 out by springs. But he gave the preference to the plan of rotating by means of a 

 simple but peculiar sort of fire-wheel behind, producing a tangential force which 

 increases the rotation when most needed. 



By using smooth cylindrical shot pointed in front and having this fire-wheel behind, 

 every large gun may be used as a rifle cannon without loss of power. 



3. He next showed that the envelope of condensed air being proportioned to the 

 extent of surface and velocity, the larger the ball, the further it may be made to go. 

 But the difficulty is that at a very great distance one projectile is likely to miss. This is 

 remedied by building the projectile of as many or as few pieces as may be required, 

 and dispersing them by centrifugal force, by exploding the zinc case at a certain part 

 of its flight. 



The principle was then applied to cannons which should be large but not rifled. 

 In that case, they may be built, the chamber cast in brass or bronze ; the barrel, a 

 tube girded by broad concentric hoops, manufactured spir^iily like gun-barrels. 



It was also suggested that the projectiles be oiled and wrapt in calico before being 

 fired ; that moveable cylinders be used in guns, so that when one is worn out another 

 may be put in ; that touch-holes be drilled in moveable rods screwed into the gun, 

 and that the screw be rim on different diameters, so ihal the enemy cannot renew them 

 if they be spiked ; and that experiments by actual gunnery be preceded by experi- 

 ments in water, which represent nearly the same phsenomena at a small velocity that 

 occur in air at a high velocity. 



On a Momentum Engine. By William Gorman. 



This engine consists of a wheel, having radial scoop-shaped vanes or blades, driven 

 round by jets or streams of fluid projected tangentially against their extremities, which 

 streams describe spiral paths by contact with the revolving blades, and are discharged 

 near the centre of the wheel where the velocity is small, after having imparted to the 

 wheel as much of their motive power as possible. 



A steam-engine on this principle was substituted for a high-pressure cylinder steam- 

 engine, was supplied with steam from the same boiler, and was set to drive the same 

 machinery, which it did in a satisfactoiy manner, although working under great dis- 

 advantages. 



The momentum steam-engine has been in regular use for nearly two years, and has 



* See Architect's and Civil Engineer's Journal for October 1855. 



