REV. WILLIAM SCORESBY, D.D.

FELLOW OF THE ROYAL SOCIETIES OF LONDON AND EDINBURGH;
CORRESPONDING MEMBER OF THE INSTITUTE OF FRANCE,

ETC. ETC.

PART II.

COMPRISING INVESTIGATIONS CONCERNING THE LAWS OR
PRINCIPLES AFFECTING THE POWER OF MAGNETIC STEEL PLATES
OR BARS IN COMBINATION, AS WELL AS SINGLY,
UNDER VARIOUS CONDITIONS AS TO MASS, HARDNESS, QUALITY,
FORM, ETC., AS ALSO CONCERNING THE COMPARATIVE
POWERS OF CAST IRON.

LONDON:

PRINTED BY MANNING AND MASON, IVY LANE, PATERNOSTER ROW.

ADVERTISEMENT

TO THE

SECOND PART

OF THE

MAGNETICAL INVESTIGATIONS.

"

THE experiments described in this second Part of Magnetical Investigations," were, to a very considerable extent, made some years ago. They have been carried forward, however, at intervals, as the Author's arduous professional duties would admit, to the present time; and the publication of the results obtained has been deferred until all the objects of inquiry, belonging to the department of experimental research, which were originally contemplated, or have been suggested in the progress of the Investigations, have been completed.

It is hardly needful to say that the researches have been of a very elaborate nature and extent. The Tables given in this part of the work alone are the result of above four thousand observations

on the deviations produced by the numerous magnetical plates and bars subjected to experiment,--each observation requiring the needle of a five-inch compass, after being disturbed by the influence of the magnet to be tested, to attain a stationary position, and the angle of deviation from the magnetical meridian, to be read off to within a minute or two of a degree. And besides this labour by the method of deviations, a large number of magnetical bars of the horse-shoe form, etc., had to be otherwise tested; and the results obtained by the different modes of experiment required to be tabulated, in many cases at a considerable addition of trouble, for reducing the observations, and for obtaining the exact measures and weights of the bars or plates employed.

Similar investigations, as some of these here described, have, as is well known, been before made, and analogous results, in certain cases, obtained. The very extensive range of inquiry here pursued, however, with a constant adherence to the same modes of experimenting and testing, will, the Author hopes, not only excuse his having gone over some ground previously examined; but will yield a measure of newness -by the unity of method and ampleness of investigation in the vast varieties of mass, form, quality, temper, and denomination of the magnets made use of-to the researches themselves.