202 report — 1860. 



of successful small ones, which had given satisfactory results in every way, except 

 that they had failed after a short time for want of strength. Mr. J. Lawrence, in 

 1855, rilled a 6|-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 4 inches bore, and sides 9 inches thick; but 

 it burst. He then tried another, 11 inches thick, and it too burst. He had, how- 

 ever, since made a stronger cannon, whose success was absolute proof that the one 

 thing wanting in the other was strength. Capt. 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 

 diffused 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 careful adjustment of the size of the layers, Capt. 

 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, Capt. Blakeley's, theory, he quoted official 

 reports 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 gim, 

 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 526 lbs. Mr. Whitworth's 

 last new 80-pounder was another instance of the successful application of Capt. 

 Blakeley's prmciple. 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, were forced by hydraulic pressure. Ex- 



Eeriments had enabled him to determine accurately what amount of pressure each 

 oop woidd 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 Capt. Blakeley's suggestion, except- 

 ing that the rings were put on too tight, which might prove a cause of weakness. 

 The method of rifling adopted by Capt. Blakeley cannot be made intelligible with- 

 out 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. Capt. Blakeley 

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

 constructed on his own plans, from which he had thrown shells to a distance of 

 2700 yards, with only 5° of elevation, which was stated to be a range 300 yards 

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



On a deep Sea Pressure Gauge, invented by Henry Johnson, Esq. 

 Head by the Rev. Dr. Booth, F.R.S., fyc. 



In deep sounding the pressure is too intense to admit of measurement by the com- 

 pression of any highly elastic fluid in a small portable instrument. Water, however, 

 possesses a slight degree of elasticity, and an instrument recording the compression 

 of an isolated portion of water by the pressure of the sea, will show the compression 

 of the water at the depth to which it has been lowered. 



Mr. Canton, who in 1761 communicated his observations to the Royal Society, 

 found in water, compressed under a glass receiver, by the pressure of an additional 

 atmosphere, a diminution in bulk equal to one part in 21,740; and in water placed 

 under a receiver a similar expansion when the air in the receiver was exhausted. 

 Mr. Perkins, more recently, found a diminution of bulk of /jths in water under a 

 pressure of 1120 atmospheres. The theory of increased pressure at great depths is 

 corroborated by a very interesting experiment made by the distinguished voyager 

 Rear- Admiral Sir James Clark Ross, who lowered, to a great depth, a bottle fitted 

 with a tube, with a cork suspended so as to enter the tube, if, as anticipated, the 

 water in the bottle, condensed under heavy pressure, should expand upon the raising 

 of the bottle and the removal of the pressure. Upon the return of the bottle to the 



