538 DR. SCHULTHESS ON THE APPLICATION OF 
(weighing 0:29 killog.): the original coil had been removed, but imme- 
diately replaced by a smaller number of coils. To this magnet (even 
after 14 days had elapsed) I could in no way communicate any appre- 
ciable magnetic power.” 
To me these statements are very enigmatical; at least I have never 
observed anything similar in my own experiments; and not only dif- 
ferent 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 wili 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 ta 
set a machine in motion at the least possible expense.” 
I must confess that I cannot from this too short and uncertain de- 
scription form any clear idea of Dal Negro’s process, and I am therefore 
very curious to see his forthcoming paper. I could only clearly under- 
stand his first method of setting a lever in motion, and I determined to 
make these experiments as soon as I had finished those which I had 
