tricity to make soft iron magnetic. In the year 1825, Sturgeon magnetized cylindrical horseshoes of soft iron by means of copper wires wound round them, connecting the ends of the wires with the plates of an electromotor. Professor Van Moll of Utrecht saw this experiment performed in the physical laboratory of the London University by Mr. Watkins, and he obtained on repetition those remarkable results described in Bibl. Univ., cah. 45. p. 19. This new method of communicating such great attractive power to iron created in me the desire of repeating the experiments, and principally of taking into consideration the application of this attractive power, which it appears may be infinitely increased, to some useful purpose. I give these experiments to the public in the conviction that a force so easily evolved and so very powerful justifies repeated and varied experiments. In my experiments the electromotors employed were without doubt smaller than any hitherto used, and these notwithstanding produced the same results: new circumstances and new laws were observed and discovered respecting the manner of increasing the magnetic power evolved by electromotors, of producing. in them currents now similar, and now different, sometimes in the same, sometimes in opposite directions, and by the success of these experiments of setting a lever in motion in different ways, and thus finally enriching natural philosophy with a new motive power."
It is easy to imagine with what avidity I read this notice, partly from joy at seeing my idea, of the practical application of which I still had many doubts, mentioned by another person, and partly somewhat vexed that the priority of my invention, if it really was as useful as my fancy made me think it, was snatched away from me. I therefore read with intense eagerness this paper; but my expectations were in a great measure disappointed; for it was only at the end that Dal Negro gave some short, and to me not altogether comprehensible hints concerning his experiments on the application of the power of electro-magnets to moving machinery, after having described a considerable number of other experiments, the principal object of which was to give with the least possible means to a soft-iron horseshoe the greatest possible magnetic power. He took seven different horseshoes, varying from 0·29 to 5 killogrammes[1] in weight: the copper wire with which he enveloped them, in from 37 to 64 coils, had a diameter of 8·2 to 8·4 mill.; the zinc plates of the four different electromotors had surfaces = ¼, ¾, 2⅓, and 4⅖ square feet each; the dilute acid employed consisted of 160 of sulphuric acid and 160 of nitric acid in 1 of water. With these electro-magnets Dal Negro obtained remarkably powerful results. The largest, (weighing 5 killog., surrounded with 64 coils of copper wire of 8·4 millim. diameter,) with the armature weighing 2 killog., when connected with the largest electromotor, supported from 1 08 up to 1 1 7 killog. Dal Negro attri-
- ↑ [1 millimetre = ·03937 English inch.
1 killogramme = 2 lbs. 3 oz. 5 dram.—Trans.]
