18 [March 13, 



I am informed by Professor Stokes, who kindly made the calcula- 

 tion, that such a disk (zone of 60) is in volume or weight 1'45 times 

 that of a sphere the sectional area of which is equal to the trans- 

 verse sectional area of the disk. Could such a disk, fired from a gun 

 of similar transverse section, be projected with sufficient cycloidal 

 rotation to maintain it in one plane, assuming it fired in a vertical 

 plane, the conditions appear favourable to dynamical effect at any 

 elevation. 



I find/ however, that when concentric and homogeneous, a disk so 

 fired from such a gun strikes a target, not in the vertical position as 

 fired, but in any position, such as broadside on ; and that it is 

 necessary for the desired effect that the centre of the gravity of the 

 disk should be slightly out of its geometrical centre, though not out 

 of the equatorial plane, and placed in a certain position in the gun. 

 I do not propose to employ eccentricity exactly as it has been em- 

 ployed in spheres, that is, to seek to gain range by the eccentricity 

 as such, but chiefly to employ merely enough of it to secure due rota- 

 tion, so as to make a disk, otherwise useless but at close quarters, 

 a virtually elongated projectile, and dependent further for its effect 

 on the more legitimate and substantial conditions of easily sup- 

 pressed windage, rotation in aid and not at the expense of trans- 

 lation, facile displacement in the gun, and several other qualities, 

 some of which are absent with spherical projectiles, and others in- 

 compatible with the rifle principle. 



In the work entitled "Shells and Shell-guns*/' by Commander 

 Dahlgren, of the United States Navy, the history of the eccentric 

 principle applied to spheres is treated at length, and by him traced 

 back to the time of Robins, or for about 100 years ; here, however, 

 a further allusion would occupy too much space, though the history 

 is an interesting one. In the fourth edition especially (or that pre- 

 ceding the last) of 'Naval Gunnery/ Sir Howard Douglas has 

 given a more minute account than has Dahlgren of the experi- 

 ments in England on this subject in 1850, 1851, and 1852, which 

 were instituted at the suggestion of Sir Howard Douglas. 



It is stated by him that it was by the experiments of General Paix- 



hans at Metz, in 1841 and 1842, the fact was first established that 



the deviations of eccentric spherical projectiles could be made to 



occur at will, either in a lateral or longitudinal direction, laterally, 



* London, Triibner and Co., Paternoster Row, 1857. 



