118 Correspondence of J. Nickles. 
rotation, a mechanical action of equal title with the preceding, and whos 
effects, produced through a subdivision like that of magnetic ola x 
are found grouped at the extremities of the axis in rotation; inthe same — 
manner as the poles develop at the extremities of a bar of iron when 
it is oem oe to torsion. : 
neto-electric machines, these magnets being much more economical on 
account of the difference in ke of cast iron and steel. The follow- 
ing are some of his conclus 
1. Gray metal gives more reaninkctcey results than white metal, which 
is moreover too brittle. 
agnets tempered ata low red heat lose all their magnetism in 
twenty: -four hou 
— ey Met ‘their magnetism perfectly when tempered at a bright 
red hea 
The “following i is the method of obtaining the maximum magnetic 
power. The bars are heated toa t in a blast furnace ; they are 
diately into a large quantity of cold water, with violent agitation. When 
the bars are cooled, they are magnetized by means of a horse-shoe 
electro-magnet capable of lifting about 200 kilograms. The two poles 
e 
this same process of friction. After operating thus upon one of the 
faces, the other is subjected to the same treatment, taking care that the 
same poles are brought into contact with the same branches 
The poles of the bundle of cast iron magnets ought to be a 
kept in contact with an armature of wrought iron of a size proportion 
al to that of the bundle. The bars of cast iron should be a little thick’ 
er than those of stee 
Ascensional force of Balloons in water.—On the 18th of last ae 
Doctor Gianetti of the mineral springs of Urezza, Corsica, made a 
o 
Lal 
1 
from the bottom in deep water; and the force of it is such that “with a 
pe to ita clock movement, which by opening or closing the facet in 
top, by which the Salsas is filled or emptied, shall cause it to rise 
a ft at will. It is also proposed to use this invention in river navi- 
