80 
FIRST REPORT — 1831 . 
is carried on with the careful avoidance of such a heat as would 
occasion the fusion of the ore; for this is ascertained to he very 
injurious to the subsequent operation.” 
It was remarked by Mr. Johnston, that a similar observation 
had been made some years ago by Professor Brodberg, of the 
school of Mines at Fahlun, and was detailed by him in a paper 
published in the Swedish Transactions, and reprinted in the 
Edinburgh Journal of Science . 
THURSDAY EVENING. 
On Thursday Evening Mr. Scoresby gave An exposition 
of some of the laws andphenomena of Magnetic Induction, and 
of the mutual influences of magnets on each other, with an ac¬ 
count of a method of application of the magnetic influences 
for the determination of the thickness of solid substances not 
otherwise measurable .—In the introductory observations, Mr. 
Scoresby considered the general nature, as far as it is understood, 
of the magnetic principle, and described a magnetic bar as a 
battery of magnetic particles, the arrangement of which being 
regular and consistent, transmits to the poles, like the galvanic 
pile, the general aggregate of their individual energies. He 
defined induced magnetism, “ as the development of the latent 
magnetism in iron or steel by the juxtaposition of any substance 
in a magnetic condition.” His investigations on the law of 
induced magnetism extended to the different qualities of iron 
and steel; to the proportion of influence acquired by similar 
masses at different distances from the proximate magnet; and 
to the relation of capacity in masses in all other respects similar 
except as to thickness. The proportion of influence was shown, 
at different distances, of the magnetism induced upon the nearer 
and more remote ends of a bar of soft iron, and the quantity 
transmitted, compared with the portion directly induced, was 
numerically stated. A bar of very soft iron, placed directly 
over a magnet of similar dimensions, w T as found at the distance 
of 5 inches, to acquire yyth of the power of the magnet. At 4 
inches above, the inductive influence of the magnet was T gth of 
its own power; at 3 inches, T ? T th; at 2 inches, ^th; at 1 inch, 
^tli. At j of an inch above, tiie power induced was equal to 1? 
that of the magnet, and at the distance of T Vth, it amounted to 
frds. Several new and curious illustrations of the phenomena 
of induced magnetism were then exhibited to the Meeting. 
FRIDAY MORNING. 
Mr. Scoresby concluded his account of his Magnetical 
experiments. He described the action of magnets of different 
