98 Notices of Books. (January, 
on to the magnetism of all bodies, discovered by Faraday in 
1845, and extended by Knoblaud, Tyndall, and others. It is 
curious, however, that the fact that a piece of bismuth repels a 
magnetic needle was remarked no less than a century ago by 
Brugmans, while Lebaillif made the same observation with 
regard to antimony in 1829. From the experiments of Tyndall 
and Weber we may conclude— 
“1, That all bodies are polarised under the action of a mag- 
netic force. 
2. That in soft iron, and other pava-magnetic bodies, the 
pole induced in the side next the inducing pole is of a 
contrary kind, and that, consequently, the body is 
attracted. / 
3. That in bismuth, and other dia-magnetic bodies, the pole 
induced on the near side is of the same nature as the 
inducing pole, and that, therefore, the body is repelled.” 
Becquerel has found that the specific magnetism of manganese 
is such as would result from the presence of 1-10coth part of its 
weight of iron, while that of gold would result from the presence 
of 1-114000th part of its weight of iron; but this latter state- 
ment is not very clear, since we find gold given in the list of dia- 
magnetic bodies. The table of results given on p. 63 is of 
special interest. It shows the quantitative relationship between 
various bodies chiefly dia-magnetic (—), with a few magnetic 
gases (+), in regard to absolute force acting on equal volumes 
and reduced to avacuum. From this we learn that while oxygen 
is +17°5, nitrogen is almost neutral on the side of attraction 
+0°3, carbonic acid is quite neutral, and hydrogen almost 
neutral on the side of repulsion, —o-1. Water rises to —g6‘6, 
sulphur to —118°0, and bismuth—the most dia-magnetic body of 
all—to —1967°6. 
The positions of the four magnetic poles, the existence of which 
was inferred by Halley, are given as follows, the determinations 
being those of Prof. Hausteen :— 
Latitude. Longitude. 
Stronger North Pole! 9 7:i2) 70° - 5" IN: gg’ 6' W. 
Weaker North Pole Leet) LNOmeha ANG TI8"-3q\ ae. 
stronger South Pole. 2... ..697 26'S. 138° 35 E. 
Weaker South Pole see, TZ) ns 120° 57 W. 
A detailed account is given of the various elements of the 
earth’s magnetism, and the methods of observing them. The 
book would be improved by good drawings of the various instru- 
ments now employed in magnetic observations. Some useful 
Curve Tables are given. ‘The whole subject is treated mathe- 
matically, and the book is a valuable contribution to our magnetic 
literature. It will be especially useful to observers and workers 
. In the numerous magnetic observatories which are now to be 
found in every part of the world. 
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