392 Progress in Science. [July, 



the results of his examination of a crystallised Bessemer slag from Hoerde. 

 Drusy cavities in the slag run out from the converters, often contain well- 

 formed crystals isomorphous with rhodonite, pajsbergite, and babingtonite, 

 and certain triclinic minerals of the augite group. The slag is a bisilicate of 

 iron and manganese, and contains — Silica, 44*73 ; ferrous oxide, 20*59; rnan- 

 ganous oxide, 3274; lime, 1*53; and magnesia, 0*17. Its specific gravity 

 was 3-08. 



ENGINEERING— MILITARY, CIVIL, AND MECHANICAL. 



Military Engineering — Field Guns. — The report has recently been pub- 

 lished of a committee which was appointed in July last for the purpose of carry- 

 ing out certain competitive trials, with the view of testing the relative 

 efficiency of muzzle and breech-loading guns for field service. Two batteries 

 were placed at the disposal of the Committee for the purposes of their 

 experiments, one consisting of three 12-pounder and three g-pounder breech- 

 loading wrought-iron guns, and the other of six 9-pounder muzzle-loading 

 bronze guns. Each gun was provided with 240 rounds, consisting of a certain 

 number of rounds of shrapnel, segment, and common shell, of case shot, and 

 of percussion and wood time fuzes. From the results of these experiments it 

 appears, that in respect of shooting, the g-pounder muzzle-loader and the 

 12-pounder breech-loader are about on a par, whilst the g-pounder breech- 

 loader is inferior to both. The advantages of simplicity, facility of repair, 

 ease of working, rapidity of fire, original cost, and cost of maintenance, are all 

 in favour of -the muzzle-loader, whilst the breech-loader possesses the advan- 

 tage of affording a superior amount of cover to the detachments when 

 entrenched and in the open. The conclusion of the Committee is that, on the 

 whole, a muzzle-loading gun is more efficient for war purposes, and they 

 recommend that, if adopted for home service, they be made of wrought-iron 

 with steel tubes. The report has been adopted by the Secretary of State for 

 War, and it may therefore be concluded that the contest, so far as this 

 country is concerned, has, for the present, been definitely settled in favour of 

 the muzzle-loader. 



Marine Heavy Ordnance. — The following description of our new 35-ton gun 

 is taken from " Engineering." The great gun consists of six. distinct parts ; 

 First, the inner or a tube, which is of Frith's steel, and is 13 feet 6\ inches 

 in length, internal measurement. The thickness of the tube is 3! inches at the 

 breech, and tapering down to i\ inches at the muzzle. Next this is the 

 muzzle or b tube/which is of wrought-iron, and is shrunk on to the steel tube. 

 The third piece forms the first-stepped joint, about 6 feet from the muzzle, and 

 is known as the intermediate coil ; it holds the front end of the coiled breech- 

 piece which forms the fourth part. The fifth part is the outer or c coil, with 

 its trunnion band, which is shrunk on to the breech portion of the gun, binding 

 the rear end of the intermediate piece. The sixth and last piece is the 

 cascable, which is made button-shaped instead of the ordinary form, in order 

 to obtain the greatest possible length of bore in the gun within a restricted 

 dimension, the Admiralty having limited the length over all to 16 feet 3 inches. 

 The vent is placed on one side of the breech piece in order to render it easily 

 accessible for firing. The gun is rifled to a calibre of n*6 inches, and the 

 length of the bore is 13 feet 6| inches. The rifling consists of nine grooves, 

 and in twist uniformly gaining from zero at the breech to 1 turn in 35 

 diameters at the muzzle. The weight of the projectile which this gun 

 is intended to carry is 700 lbs. ; the length of the solid shot being 30 inches, 

 and that of the common shell 40 inches ; the shell carries a bursting charge 

 of 38 lbs. 



Breech-loading Rifles. — On the 27th April last, a paper was read before the 

 Institution of Mechanical Engineers, by Mr. W. P. Marshall, on " The Prin- 

 cipal Constructions of Breech-loading Mechanism for Small Arms, and their 

 Relative Mechanical Advantages ; Illustrated by Specimens of Breech-loading 

 Rifles." Mr. Marshall stated that breech-loading guns were first adopted by 

 the Prussian army : the celebrated needle gun having been in use for more 



