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XV. On the Difference in the Magnetic Properties of Hot-Boiled and Cold-Boiled 
Mallecible Iron, as regards the power of receiving and retaining Induced Magnetism 
of Subpermanent Character. By Geoege Biddell Aiet, Astronomer Boijal. 
Eeceived April 22, — Eead May 15, 1862. 
In reflecting on the difierences exhibited by different iron-built ships in the change of 
their subpermanent magnetism, it has often occurred to me as a subject worthy of 
experimental investigation, whether a portion of this difference might not depend on 
the temperature at which the plates of iron are passed through the rollers in the last 
stage of their manufacture. No favourable opportunity of making these experiments 
presented itself until, in the course of the last winter, I became aware that Mr. Faie- 
BAIEN had been engaged in experiments on the difference of the strength of plates of 
malleable iron, according as they had been rolled at a high or at a low temperature. I 
immediately requested Mr. Faiebaien’s kind offices for procuring for me bars adapted 
to magnetic experiment, divided into the four classes of — 1. Hot-Boiled, with the length 
of the bars parallel to the direction in which the rolling had lengthened the iron, or 
parallel to the direction of fibre ; 2. Hot-Eolled, with the length of the bars transverse 
to the direction of fibre ; 3. Cold-Kolled, with the length of the bars parallel to the 
direction of fibre ; 4. Cold-Boiled, with the length of the bars transverse to the direc- 
tion of fibre (which classes will hereafter be described by the words, 1. Hot-Boiled Lon- 
gitudinal; 2, Hot-Bolled Transversal; 3. Cold-Boiled Longitudinal; 4. Cold-Boiled 
Transversal). Upon Mr. Faiebaien’s application, the bars which I requested were 
promptly and gi-atuitously furnished by Bichaed Smith, Esq., Superintendent of Loed 
Dudley’s Iron AYorks at the Bound Oak Works near Dudley. 
The number of bars was 24, namely, 6 in each of the four classes above described. 
Each bar was 16 inches long, 4 inches broad, and about inch thick: the aggregate 
weight of the bars in each class w’as, — 1st, 28 lbs, 8 oz. ; 2nd, 28 lbs. 10 oz. ; 3rd, 27 lbs. 
10 oz. ; 4th, 27 lbs, 8 oz. The manufacture of the bars is described to me in substance 
as follows : — The hot-rolled and cold-rolled bars were all manufactured in the same way 
up to the stage of producing sheets of iron of the desired thickness ; the last rollings 
having commenced with large bars at a welding heat, and having terminated with the 
bars (now converted into sheets) at a dull red heat. Then the sheets to be cold-rolled 
were allowed to cool to a perfectly cold state, and in that state were rolled afresh 
between other rollers. After this, the experimental bars were cut out of the sheets. 
Each set of six bars was packed in one box, with the maker’s inscription on every bar 
reading forward in the same direction in all. 
The bars when received by me, after resting some days in a room, were all placed 
MDCCCLXII. 2 P 
