48 
The Australasian Scientific Magazine. [Sept, i, 1885. 
Illipe Erskineana. 
F. v. M. in Melbourne Chemist, April 1885. 
South Cape ; Rev. J. Chalmers and Rev. W. Gill. 
Since the description of this economically important species was 
published, the telling work of the Rev. Will. Wyatt Gill and the Rev. 
James Chalmers (on their missionary travels in New Guinea from 
1877-1885) has reached me, in which at p. 329 is referred to the Poti-Poti 
as an umbrageous tree, attaining sixty feet in height, and yielding a 
globular one-seeded fruit as much as three inches diametrically wide, of 
apple-smell and agreeable peculiar taste. 
( To be continued.) 
COMPLEMENTARY MAGNETISM. 
BY 
HERR R. VON HAAP. 
A magnet has aptly been described as a steel bar in a cyclone of 
electricity. Cut the bar in two and (the whirlwind continuing) each piece 
becomes a magnet. Magnetise a ring, and the whirlwind is spent upon 
itself, and no magnetic action is shown. Break the ring, and the latent or 
rather neutralised magnetism becomes active. 
The tendency of a bar magnet to point towards the poles and dip 
according to the latitude, is well understood. But there is another 
magnetic force so rare in its occurrence, and so slight in its power, as to 
be neutralised by the former forces. This is the sympathy of complemen- 
tary magnets. 
In my travels in India I learnt a great deal of the so-called magic of the 
“ Mahattmahs ” or professional conjurers of that country. And I am 
forced to the conclusion that much of their doings that excite such 
wonder is simply the use of an extended knowledge of sciences we 
possess. It was here (at Cawnpore), that I first saw one of a pair 
of complementary magnets used for telegraphing, to the great wonder 
and awe of the natives, who saw in it something supernatural. 
These magnets, I afterwards learnt, are prepared by first magnetising a 
straight steel bar, tempered to a perfectly even hardness, and then cutting 
it exactly in half. Now, to neutralise the tendency to point and dip to the 
