Page:Scientific Memoirs, Vol. 1 (1837).djvu/550

538 (weighing 0·29 killog.): the original coil had been removed, but immediately replaced by a smaller number of coils. To this magnet (even after 14 days had elapsed) I could in no way communicate any appreciable magnetic power."

To me these statements are very enigmatical; at least I have never observed anything similar in my own experiments; and not only different horseshoes of soft iron, but several varieties of hardened steel have always appeared to me very susceptible of electro-magnetism; steel of course in a less degree than iron, but notwithstanding much more so than I had expected from the observations of others. Every time when in my experiments no action was observed, or at most only a very feeble action, I found that either the circuit was somewhere interrupted, or the battery was too weak.

I was most interested by the last portion of Dal Negro's paper; it is as follows:

"As I had been successful in producing temporary magnets of very great power with very small electromotors, I endeavoured to apply this new power to moving machinery. I will now briefly state by what means I endeavoured to set a lever in motion. I first used a magnetic steel bar, placed vertically beneath one end of a temporary magnet: the bar vibrated from the attractions and repulsions which took place between its south pole and the north and south poles of the electro-magnet. In the same way a motion may be effected in a horizontal plane. I also set in motion a similar bar, by allowing a piece of iron, set free from the magnet at the moment when its power became = 0, to fall on one of its ends; after this it was immediately re-attracted. This can be effected in two ways; the one may be employed when a quick motion is to be produced, and the second when a greater force is wanted: in the first case the weight falls only just out of the power of the magnet's attraction; and the instant the weight has fallen upon the bar or lever, it is re-attracted by the magnet that the action may be repeated: this weight is always very small in comparison with that which the magnet can support whilst in contact. In the second case the whole weight which the magnet can carry is employed, and use is made of the force which draws it to the magnet. This can be done in several ways. One of them forms a very powerful electro-magnetic ram. I shall not fail to make known the action of this new machine, and hope thereby to satisfy those in particular who are endeavouring to set a machine in motion at the least possible expense."

I must confess that I cannot from this too short and uncertain description form any clear idea of Dal Negro's process, and I am therefore very curious to see his forthcoming paper. I could only clearly understand his fast method of setting a lever in motion, and I determined to make these experiments as soon as I had finished those which I had