ARTILLERY 



235 



Table showing the Increase of Density in Castings of large Size, due to their Solidifi- 

 cation under a Head of Metal, varying from two to fourteen Feet : 



The experiments were made upon cylindrical shafts of cast-iron, cast vertically in 

 dry sand-mould, under heads gradually increasing up to fourteen feet in depth, and 

 all poured from ' gaits ' at the bottom. 



These experiments show an increase of density due to fourteen feet head, about 

 equal to a pressure of 44'8 Ibs. per square inch on the casting; from 6-9551 to 7*1035 

 for Scotch cast-iron. 



About the latter end of 1854, the attention of Mr. Kobert Mallet, C.E., was directed 

 to the mathematical consideration of the relative powers of shells in proportion to 

 their increase of size or of diameter. His inquiries resulted in a memoir presented 

 by him to Government, in which he investigated the increase of power in shells with 

 increase of diameter, under the heads of: 1. Their penetrative power. 2. Their 

 increased range and greater accuracy of fire. 3. Their explosive power. 4. Their 

 power of demolition, or of levelling earthworks, buildings, &c. 5. Their fragmentary 

 missile power. 6. and lastly, their moral effect, in every case viewing the shell, not 

 as a weapon against troops, but as an instrument of destruction to an enemy's works. 

 The result so convinced Mr. Mallet of the rapid rate at which the destructive powers 

 of a shell increase with increase of size, that he was induced to propose to Govern- 

 ment the employment of shells of a magnitude never before imagined by any one, 

 namely, of a yard in diameter, and weighing, when in flight, about a ton and a quarter 

 each : and to prepare designs, in several respects novel and peculiar, for the construc- 

 tion of mortars capable of projecting these enormous globes. Such a mortar was 

 made, and on the 19th of October, 1857, tho first of those colossal mortars, constructed 

 from Mr. Mallet's design (jig. 91), was fired on Woolwich Marshes, with charges (of 

 projection) gradually increasing up to 70 Ibs. ; and with the latter charge a shell 

 weighing 2,550 Ibs. was thrown a horizontal range of upwards of a mile and a half, to 

 a height of probably three-quarters of a mile, and falling, penetrated the compact and 

 then hard dry earth of the Woolwich Eango to a depth of more than 18 feet, throwing 

 about cartloads of earth and stones by the mere splash of the fall of the empty shell. 



