SHORT NOTES ON PROFESSIONAL SUBJECTS. 
17 
23. Iron plate experiments. The following extract from a letter 
addressed by the Enssian Minister of Foreign affairs to the British Ambassador 
will be read with interest— 
Sx Petersburg-, 
Le || Mai, 1867. 
M. le Vice Chancelier n’a pas manque de placer sons les yeux de S. M. 
l’Empereur, et de transmettre a M. le Ministre de fa guerre, le remarquable rapport 
du Capitaine Noble sur Faction comparative de differents projectiles, que Y. E. a 
eu l’obligeance de lui communequer par la note du JJ- Mars, 1867. 
C’est avec le plus vif interet que 1’ aide-de-camp General Militaire a accueilli 
ce travail, si digne a tous egards de fixer 1’attention des hommes speciaux, et il se 
fait un plaisir, conformement au desir exprime par Y. E. de mettre a la disposition 
du Gouvernement Britannique le resultat des differentes experiences faites en 
Eussie avec des canons se chargeant par la culasse, ainsi que deux memoires du 
General Major Mayefski, qui traitent de F influence rotatoire des projectiles sur 
leur force d’impulsion. 
The memoirs of General Mayefski (of the Eussian Committee of Artillery), above 
referred to, are,— 
(1) De Vinfluence du mouvement de rotation sur la trajectoire des projectiles 
oblongs dans Vair, pp. 183 : extracted from Yol. Y. of the Revue de Technologie 
Militaire > 1865. 
(2) De Vinfluence du mouvement de rotation des projectiles oblongs sur leur 
trajectoire dans les milieux solides, pp. 105 : extracted from the same work. This 
latter is the paper reviewed by Mr Mallet in the “ Engineer 55 of January 1867, as 
noticed ante No. 8. 
24. Erosion of the bore of rifled guns firing battering charges^ 
The effect produced upon the upper surface of the bore of a rifled gun firing 
battering charges is to produce a disintegration of the metal which shews itself first 
in narrow longitudinal striae, such as might be produced by a comb of unequal teeth 
moved irregularly. These longitudinal markings are next connected by very fine 
transverse lines at right angles to them, at tolerably uniform intervals, giving a 
reticulated appearance to the whole surface. Then as firing is continued the 
longitudinal channels deepen and become more and more irregular, the gas eating 
out cavities of rounded section and irregularly connected, until after 400 or 500 
rounds, a gutta-percha impression exhibits deep irregular channels diversified with 
lumps and knobs that at a little distance resemble the bark of a tolerably rugged 
tree more than anything else. It will be easily seen that this effect depends 
almost entirely on the amount of the charge. The quantity of gas trying to escape 
between the upper surface of the shot and the bore of the gun increases in a much 
higher ratio than is expressed by the weight of the charge in lbs.; the original 
smoothness of the surface is sooner broken through, and gutters formed; and 
these gutters once formed, there is more heat and pressure tending to wear them 
deeper. It has consequently become a great object to try and check the flow of 
gas. One obvious way is to vent the gun and ignite the charge on the under side, 
but there are some practical difficulties in the way of this plan, and experiments 
have for some time past been in progress with wads of different materials. Of 
these the best has proved to be a wad of papier macJie made a close fit, and cut to 
enter the grooves. It weighs for a 9-in. gun about 2 lbs. The good effect of 
using it has been remarkably illustrated by comparing the condition of the bore of 
4 
