Experiments and observations on the development of magnetical properties in steel and iron by percussion:—Part II
After adverting to the general results of his former inquiries, the author observes that his principal objects on the present occasion were to endeavour, by auxiliary rods of iron, to increase the degree of magnetism; and to ascertain on what circumstances, as to the magnitude of the iron rods, and the quality, size, and temper of the steel wires, the utmost success of the method depends. He formerly used a single iron rod, upon which the steel bars were hammered, both being in a vertical position. He now places the steel wire between two rods of iron, and subjecting it, through the medium of the upper rod, to percussion, derives the advantage of the magnetism of both rods of iron acting at the same time upon both its poles. The rods he used were of the respective lengths of three and one foot, and an inch diameter; and the upper end of the larger rod and the lower one of the smaller rod were made conical, there being an indentation in each to receive the ends of the steel wire. Some magnetism was then elicited by percussion in the larger rod, and the steel wire being properly placed between its upper extremity and the lower one of the small rod, the upper end of the latter was hammered, and magnetism thus communicated to the wire; whilst the lower rod, receiving some influence from the percussion, performed a similar office. The author calls this mode of proceeding, the compound process , to distinguish it from the mere hammering of the wire upon the rod, as practised by him formerly, and which he terms the simple process . He then enters into extended details of his several experiments, of which the following are the principal results: first, that the compound process is more effectual in the production of magnetism than the simple one , though the ratio of augmentation does not appear determinate. In one experiment, the maximum effect of the simple process was an attractive force capable of lifting between 186 and 246 grains, while the compound process augmented the lifting power to 326 grains. In another, the simple process gave a lifting power of 246 grains, the compound of 345 grains. Moreover, the efficacy of the compound process is much less manifest upon long than short wires, and is greatly impaired by diminishing the size of the rods.