MECHANICS AND USEFUL ARTS. 57 



sure, the breech portion receiving hoops of puddled steel. The small TVhit- 

 wm-th guns undoubtedly possess the great advantage of simplicity of con- 

 struction over the compound guns just described; but the present great ex- 

 pense of the material gives the latter the advantage in point of cost. There 

 can lie little doubt, however, that the facilities for obtaining products of this 

 description will increase with the demand; and there appears no reason why 

 the process of Mr. Bessemer, which has recently been applied with great 

 success to the conversion of iron of good chemical quality into excellent 

 cast stce!, upon a very considerable scale, should not be resorted to for the 

 production, at a moderate cost, of masses of cast steel, or a material of a 

 similar character, of sufficient size for conversion into cannon of all sizes 

 but those of the heaviest calibre, which it will, perhaps, always be found 

 most advantageous to construct of several pieces, upon the principles just 

 now referred to. 



The improvements effected in the construction of fire-arms have rendered 

 indispensable a careful revision of the descriptions of gunpowder hitherto 

 used, which has already led to the modification of several important points 

 in the manufacture of powder, whereby a greater uniformity in the action of 

 the latter is ensured, and its explosion is regulated with especial regard to 

 the double woi'k which it now has to perform in the greater number of rifled 

 arms, namely, that of propelling the projectile, and of expanding it into the 

 grooves of the rifle. 



Considerable attention has been devoted in different continental states, 

 during the last few years, to the application of the different forms of elec- 

 tricity to the discharge of mines. The many serious inconveniences attend- 

 ing the employment of voltaic batteries for that purpose in the field, have 

 led to the use, with considerable success, of the arrangements contrived by 

 Ruhmkorff and others for the production of powerful electro-magnetic cur- 

 rents. The application of the induction-coil machine, with appropriate fuse 

 arrangements, for the ignition of the mine by means of the spark, led to a 

 very great reduction in the size of the battery required even for extensive 

 operations. The necessity, howcvefr, of still using a battery, and the great 

 liability to injury of the induction apparatus, have rendered the advantage to 

 be attained by their employment somewhat questionable. In Austria very 

 important results are said to have been obtained by the employment of fric- 

 tional in the place of voltaic electricity. A very portable arrangement of a 

 plate-electric machine, with Leyden jars, and a small stove to protect the 

 apparatus from damp, has been employed with success in some extensive 

 operations, as many as one hundred charges having been fired simultaneously 

 by its means. Professor Wheatstone and Mr. Abel have carried on numer- 

 ous experiments on the application of electricity in this direction; and, at the 

 suggestion of the former, attempts were made to employ the electricity ob- 

 tained by induction from permanent magnets. No difficulty was experienced 

 in igniting a single charge by its agency; but it was found that the ignition 

 of more than one charge could not be effected with certainty "by the employ- 

 ment even of the most powerful magnets and the use of fuses containing 

 very sensitive compositions. Eventually, a fuse arrangement was contrived 

 and a composition prepared by Mr. Abel, with the employment of which the 

 ignition of several mines could be effected with certainty, by means of one 

 of the small magnetic arrangements employed by Mr. Wheatstone in his 

 portable telegraphs; and an ingenious combination of several such magnets, 

 arranged in a form very portable and readily worked by any soldier, can be 



