TRANSACTIONS OF THE SECTIONS. 33 
The principal maximum occurs about two hours after the moon’s passage of the infe- 
rior meridian ; a secondary minimum about four hours before the passage of the su- 
| perior meridian ; a secondary maximum about one hour after the superior passage ; 
and the principal minimum about six hours and a half after that passage. 
Curves were exhibited illustrating these results, and also the diurnal motion of a 
magnetic needle freely suspended in the direction of the magnetic force. From the 
: latter some curious results have been deduced, which will be found elsewhere, It will 
be enough to mention, at present, that in the mean for the year, the motion from 6 p.m. 
till 6 a.m. is very trifling ; between midnight and 6 a.M. the needle is almost stationary, 
nearly the whole motion occurring between 6 a.m., Noon, and 6 p.m. The end of the 
needle describes an ellipse whose major axis is at right angles to the magnetic meridian ; 
but the direction of this axis varies throughout the year. 
Magnetic Causation. By G. TowLer. 
Magnetic phenomena are due to two distinct classes of forces, which, in the absence 
of more appropriate terms, may be called the “intrinsic” and “contingent.” It is to 
the consideration of the intrinsic forces that this paper is directed. The “intrinsic” 
forces of the magnet are due, first, to the mechanical structure of the bodies in which 
magnetical phenomena are displayed, the capacity of the interstices of which bears a 
given ratio to the dimensions of the particle of fluid constituting atmospheric air, by 
and through which such interstices become highly sensitive conductors of atmospheric 
air; and, secondly, to the fluxion through and circulation round a magnetic bar of the 
particles of atmospheric media. 
The following are among the propositions which the author regards as established :— 
Each extremity of a magnet perpetually exercises the same power over the other 
that each does over indifferent masses of iron; in other words, one-half of a magnet 
is constantly magnetizing the other. 
The “intrinsic” attribute, or sine qua non of a magnet, is the extreme sensibility 
of the fluid particles in its interstices to motion, from minute forces, arising from the 
mechanical conformation of magnetical substances; and the extremities, or opposite 
forces of the body, being within that distance of each other, whereby the forces gene- 
rated by such action are sufficient to reproduce it. 
On the Results of an extensive Series of Magnetic Investigations, including 
most of the known varieties of Steel. By W. PETRIE. 
On the Process of Manufacture to produce permanent Magnets having the greatest 
_ fixity and capacity conjointly secured.—\st. The original iron—should be the purest 
soft iron charcoal made (not coke) ; the Swedish from the Dannemora mine is better 
than any other. 2nd. Converted—with pure charcoal; it should be carbonized 
lightly, the process to be stopped when the bars, of the usual size, are scarcely steel 
through, yet so that it will harden with certainty without an undue heat. 3rd. Sorted 
_ —with attention to homogeneous conversion, &c., according to the ordinary rules. 
_ 4th. Melted—the pot kept covered, and not longer than necessary in fusion. 5th. 
__ Cast—into a large ingot, so as to allow of its being weld rolled out singly, before it 
_ becomes reduced to the requisite thinness. 6th. Rolled—while hot from casting, to 
| save a second heating. It should not be doubled over nor sheared and faggofed. 
_ The rolling should be conducted at as low a temperature as convenient, as it thereby 
_ acquires a harder and closer texture and finer grain. 7th. In cutting—into shape, 
the substance (if large or of varied form) should not be strained, as by boring with 
rimers, or straightening (oftener than is unavoidable) with the hammer, as it is 
then apt to warp and to have unseen commencements of cracks on becoming subse- 
quently hardened. 
_ More carbonization than that previously described as best is of little injury to the 
_ magnetic goodness of the steel, provided it be so prepared as to preserve a homo- 
geneous and white appearance of fracture when hardened, which is not so easily ma- 
_naged as with that of lower carbonization ; but if it be again carbonized more than 
“usual (as razor steel, or above that) it rather improves; and again, an increase dete- 
‘Tiorates it as in cast iron, and a further increase again improves it. In short, in the 
1846. D 
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