The Pacific commercial advertiser. [volume] (Honolulu, Hawaiian Islands) 1856-1888, 1863-07-16
Improvements in COmpasses.

Mr.. f.. ;. Richie, of Boston, with whom Mr..
John Kehew. has recently formed 4 business
connection, has made some improvements in the
construction of cUmpasses, which are exciting
the attention of both scientific and practical men.
Patents have been secured both in this country
and England, and his invention will soon come
into general use. We make an extract from the
records of the Mass. Institute of Technology, at
its first meeting as a Society of Arts, held in
December last
It is we'll known that the liquid boat compass
Us usually constructed of late years has its bowl
filled with 4 mixture of alcohol and water, with
the view of s~teadying the movement of the card
and preventing TIN Sc violent oscillations TO which
it would otherwise be subject III a rough sea.
But it has been found that the chemical action
of the liquid greatly impairs the value of this
arrangement, as well by injuring the needles as
by obscuring the liquid and the card, 10y the de-
posit of oxide of iron. Moreover, the considera-
bic weight of the metallic card used, made IL
necessary, in order TO prevent the wearing of the
pivot. to point it with Irid-Osmium, which, from
its excessive hardness. rapidly drilled into the
agate cap, causing great friction.
lie was 20 obviate these difficulties that MIR.
Richie directed his attention to the subject.
The remedy which first suggested itself was to
coat the needles with copper, by the electrotype
process, and then To cover them with tin. This
he found practicable without injury to the mag
netism of the needles; but although the protec-
ton was good for a time, it failed eventually
from difficulty Of securing q permanently impene-
trable covering. He was led TO devise an entire
ly new plan both as regards the protection and
the suspension Of the needles, of which the
specimen compass exhibited by him was an
illustration.
In this arrangement the needles are enclosed
in a shallow cylindrical box of thin metal made
perfectly water-tight and occupied by air. The
needles are of course fixed in parallel equidistant
positions on opposite sides of the centre, and are
made 10 stand ~edgewise in the case, which by an
appropriate concavity at the centre rests upon
the pivot. In this way the needles are removed
from all chance Of contact with the liquid while
by the buOyant action of the case the pressure on
the pivot is reduced SO far as to make the friction
almost insensible, so that the pivot does not re-
quire to be delicately pointed, and the use of
Irid-Osmium becomes unnecessary. At the same
time the large surface which the case presents to
the liqnid contributes very effectualiy by friction
NJ and cohesive resistance 10 prevent sudden
movements and great oscillations even in the
most extreme agitation of the boat.
These several advantages of entire protection
from corrosion. greatly diminished friction, and
increased steadiness of the card, having been
proved by satisfactory trials in actual service,
the Navy Department at Washington is now sub
stituting the compass manufactured by Mr..
Ritchie for the old compass in a number of our
national vessels.