M3CHANICAL AND USEFUL ARTS. 49 



short time for want of strength. Mr. J. Lawrence, in 1S55, rifled 

 a GA-inch gun with three shallow broad grooves, like an Enfield, and 

 fired a lead and zinc bullet, like the Enfield. At an elevation of 5°, 

 the range was 2600 yards — 150 more than Sir W. Armstrong's ; 

 but the gun burst after about 50 rounds. Mr. Whitworth, after 

 making some excellent small arms and nine-pounders, tried a large 

 gun with four inches bore, and sides nine inches thick ; but it burst. 

 He then tried another, eleven inches thick, and it, too, burst. He 

 had, however, since made a stronger cannon, whose success was ab- 

 solute proof that the one thing wanting in the other was strength. 

 Captain Blakeley explained his own method of obtaining strength, 

 which consists simply of building up the gun in concentric tubes, 

 each compressing that within it. By this means the strain is dif- 

 fused throughout the whole thickness of the metal, and the inside is 

 not unduly strained, as in a hollow cylinder made in one piece. 

 As the whole efficacy of the system depended entirely on the care- 

 ful adjustment of the size of the layers, Captain Blakeley said he 

 was not astonished that Sir W. Armstrong had lately failed utterly 

 in his attempts to carry it out, because he did not put on the outer 

 layers and rings with any calculated degree of tension: "they 

 were simply applied with a sufficient difference of diameter to secure 

 effectual shrinkage," to quote his own words at the Institution of Civil 

 Engineers. To show that the late failure by Sir W. Armstrong did 

 not disprove his (Captain Blakeley's) theory, he quoted official re- 

 ports of a trial of a nine-pounder made by himself in 1855, which 

 showed an endurance sevenfold that of an iron service gun, and 

 threefold that of a brass gun ; as well as of an 8-inch gun, from 

 which bolts weighing 4 cwt. had been fired ; and of a 10-inch gun 

 which had discharged bolts weighing 5261b. Mr. Whitworth' s last 

 new 80-pounder was another instance of the successful application 

 of Captain Blakeley's principle. To quote Mr. Whitworth's own 

 words, — "It was made of homogeneous iron. Upon a tube having 

 an external taper of about one inch, a series of hoops, each about 20 

 inches long, was forced by hydraulic pressure. Experiments 

 had enabled him to determine accurately what amount of pres- 

 sure each hoop would bear. All the hoops were put on with the 

 greatest amount of pressure they would withstand without being 

 injured. A second series was forced over those first fixed." This 

 gun was so made at Captain Blakeley's suggestion. 



Captain Blakeley's method of rifling cannot be made intelligible 

 without a diagram ; but it may be described as a series of grooves 

 of very shallow depth, so arranged as to exert a maximum force in 

 the direction of the rotation of the bullet with a minimum force in 

 a radial or bursting direction. Captain Blakeley exhibited in the 

 court of the building in which the Section met, a 56-pounder, con- 

 structed on his own plans, from which he had thrown shells on Mr. 

 Bashley Britton's system to a distance of 2760 yards, with only 5° 

 of elevation, which was stated to be a range 200 yards greater than 

 that of Sir W. Armstrong's 80-pounder. 



Mr. Scoffern said, he thought Captain Blakeley had proved his 

 D 



