442 
POPULAR SCIENCE REVIEW. 
purposes, had a large horse-shoe magnet made, consisting of ten laminae of 
perfectly homogeneous steel, each weighing ten kilogrammes, he suspended 
it to a hook attached to a strong beam, and, having wound copper wire 
around each of the legs, which were turned downwards, he put the latter 
into communication with a battery of fifty of Bunsen’s elements, by which 
means the horse-shoe might be magnetised either positively or negatively, 
at pleasure. The variations were indicated by a small horizontal needle, 
situated in tlie plane of the poles. There was, further, a series of iron 
plates, which could be separately applied to each of the laminae. Before 
attaching any of the latter, the electric current was driven through the 
apparatus for a few minutes, and then interrupted, whereby the magnet 
acquired its first degree of saturation, marked by a certain deviation of the 
needle. One of the iron plates (usually called contacts ”) was then put 
on, and it supported a weight of 140 kilogrammes. A second trial was now 
made ; and the current having passed through again for a few seconds, it 
was found that the horse-shoe would support 300 kilogrammes, instead of 
140, The number of contacts being now increased to five, which together, 
in the natural state, supported 120 kilogrammes, it was found, after the 
passage of the current, that they could support the enormous weight of 680 
kilogrammes, which they did for the space of a full week. No sooner, how- 
ever, were the contacts taken off than the horse-shoe returned to its usual 
permanent strength of 140 kilogrammes. This tends to show that magnetism 
may be condensed like electricity for a short period. 
A new form of Manometric Barometer. — An appliance has been recently 
devised by Mr. B. Hunt, which is not startlingly novel. It chiefly consists 
of a metallic lens formed by two very thin membranes, and having a glass 
tube connected to any part of its circumference. If tliis lens be filled with 
liquid and submitted to an external pressure the liquid which fills the same 
will be forced into the glass tube to a distance which will be longer in pro- 
portion as the internal diameter of the glass tube is smaller than the volume 
of the lens. The latter is enclosed in a case connected by means of a pipe 
with the pressure to be indicated. If the pressure to which the lens is sub- 
mitted externally does not deflect the membranes beyond the limits of their 
elasticity, as soon as the pressure ceases they will return to their original 
position, and the liquid will re-enter the lens. 
Mofjnctic Variation on the Shores of Lake Superior. — The Scienti/ic Ameri- 
can, quoting one of the local papers, makes the following statement, which 
deserves attention and demands confirmation : The magnetic compass, on 
tlio north shore of Lake Superior and particularly in surveying around 
Duluth, is a very zig-zag kind of guide. The assistant surveyor in charge 
of tlie transit on the I'hwn Site Survey recently experienced some of its 
wildest eccentricities of variation. In running and cutting out a transit 
line between sections on the mountain side, at a certain spot he noticed in a 
distance of fifty feet a change from 11 degrees east to 17 degrees east; 
then in a hundred feet further back to 12 degrees east; while five hun- 
dred feet further on from 12 degrees 30 minutes cast it whirled around to 
‘K) degrees west (!) and Icept at that for three hundred feet, and then got 
back again to 1 1 degrees ea‘^t. The surveyor picked up a piece of rock of 
the granitic species, wl)ich seemed to prevail in the locality, and applied it 
