58 REPORT—1843. 
Not the least interesting part of this volume consists in the notices at To- 
ronto of auroral phenomena accompanying the extraordinary magnetic dis- 
turbanees. They are many and remarkable, and can hardly fail to throw 
great light on this branch of the general subject. 
This is not the proper place for theory, nor is anything more than an ana- 
logical illustration intended, if we compare the affections in question to what 
might be supposed to occur if we conceived the earth surrounded, besides the 
ocean and the air, with an electric atmosphere of excessive elasticity and mo- 
bility, in which were propagated from origins unknown to us, undulatory 
movements of every order, from the most minute local oscillations to waves 
affecting (almost in an instant, or in very short intervals of time, but varying 
in depth and amplitude with the geographical coordinates) its whole extent. 
Could such electric waves* be conceived as affecting the magnet, we might, 
form some idea of the mode in which particular shocks thin off as it were by 
distance of place, and are replaced by others of different local origin. 
The difficult subject of the determination of the earth’s magnetic force in 
absolute measure has been subjected to a further investigation by Dr. Lloyd. 
The difficulty, which is of a practical rather than a theoretical nature, arises 
from this, that the expression for the tangent of the angle of deflection of one 
magnet by another being expressed approximately by two terms of a series 
according to descending powers of their mutual distance, viz. the inverse cube 
and fifth power, with unknown coefficients, these have to be determined in 
Gauss’s method by observations of deflection at two different distances, and 
by eliminations, in which process serious errors are introduced in the result 
by small errors in the observations. The object of Dr. Lloyd's present paper 
is to point out a means by which the quantity sought may be obtained with- 
out elimination, by observations at one distance only, thus diminishing both 
the trouble of the observation and increasing the accuracy of the result. This 
method depends on the assumption of an empirical law in the distribution of 
free magnetism in a magnetised bar inferred by Biot from Coulomb’s re- 
searches, in virtue of which a simple ratio, dependent only on the lengths of 
the two magnets, subsists between the coefficients of the inverse powers above 
mentioned,—a ratio such, that on a certain simple assumption of the propor- 
tional lengths, the term depending on the inverse fifth power may be made 
to vanish ipso facto, and thereby get rid of the whole difficulty. Dr. Lloyd 
adduces several experiments confirmatory of these results. 
The ‘Annalen fur Meteorologie, Erdmagnetismus und verwandte Gegen- 
stiinde,’ published by M. Lamont with the assistance of Messrs. Griinert, 
Koller, Kreil, Lamont, Pleiniger, Quetelet, and Stieffel, for the year 1842, is 
completed, and will be followed up by similar series in quarterly parts. In 
this collection are contained a multitude of important contributions to these 
subjects from all quarters, and more particularly magnetic observations from 
Munich by M. Lamont; and meteorological registers from Marseilles by M. 
Benjamin Valz, from Schlésse by M. Bayer, from Dorpat by M. Madler, from 
various stations in Labrador and Greenland, from Utrecht by M. Van Rees, 
from Munich by M. Leonhardt, and a series of comparative observations from 
Stuttgard, Giessen, Carlsruhe, Vienna, and Parma, in which the barometric 
and thermometric observations are not stated absolutely, but only their dif- 
* It is by no means necessary in this way of conceiving the subject, to assume an atmo- 
sphere of pure electricity (of which we can form no conception). But we may, for hypo- 
thesis sake, admit the existence of an atmosphere of some medium very much more rare and 
elastic than air, by whose compressions and dilatations electricity may be momentarily deve- 
loped and absorbed, as caloric is by those of air in the phenomena of sound, manifesting 
itself by its action on the magnet, and' possibly by auroral pulsations also, of which latter 
phenomenon it seems excessively difficult to give any other account.—(H.) 


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