342 
New Patents and Mechanical Inventions . 
steel and form for a compass-needle, 
and is concluded by the following de¬ 
ductions : 
1. That the best material for compass- 
needles is clock spring; but care must be 
taken in forming the needle to expose it as 
seldom as possible to heat, otherwise its 
capability of receiving magnetism will be 
much diminished. 
2. That the best form for a compass- 
needle is the pierced rhombus, in the pro¬ 
portion of about five inches in length to 
two inches in width, this form being sus¬ 
ceptible of the greatest directive force. 
3. That the best mode of tempering a 
compass-needle is, first to harden it at a 
red heat, and then to soften it from the 
middle to about an inch from each extre¬ 
mity, by exposing it to a heat sufficient to 
cause the blue colour which arises again to 
disappear. 
4. That in the same plate of steel of the 
size of a few square inches only, portions 
are found varying considerably in their 
capability of receiving magnetism, though 
not apparently differing in any other re¬ 
spect. 
5. That polishing the needle has no effect 
on its magnetism. 
6 . That the best mode of communicating 
magnetism to a needle, appears to be by 
placing it in the magnetic meridian,joining 
the opposite poles of a pair of bar magnets 
(the magnets being- in the same line) and 
laying the magnets so joined flat upon the 
needle with their poles upon its centre ; 
then having elevated the distant extremi¬ 
ties of the magnets, so that they may form 
an angle of about two or three degrees 
with the needle, they are to be drawn from 
the centre of the needle to the extremities, 
carefully preserving the same inclination, 
[Nov. \ r 
and having joined the poles of the magnets 
at a distance from the needle, the operation 
is to be repeated ten or twelve times on 
each surface. 
7. That in needles from five to eight in¬ 
ches in length, their weights being equal, 
the directive forces are nearly as the 
lengths. 
8 . That the directive force does not de¬ 
pend upon extent of surface, but in needles 
of nearly the same length and form, is asv 
the mass. 
9. That the deviation of a compass 
needle occasioned by the attraction of soft 
iron, depends, as Mr. Barlow has advanced, 
on extent of surface, and is wholly inde¬ 
pendent of the mass, except a certain 
thickness of the iron, amounting to about 
two-tenths of an inch, which is requisite 
for the complete developement of its at¬ 
tractive energy. 
The same able philosopher, in a no¬ 
tice respecting a volcanic appearance in 
the moon, states that on Sunday even¬ 
ing, the 4th of February, 1821, the 
moon being two days old, and the 
evening clear, he observed a lumi¬ 
nous spot in the dark part of her 
orb ; its appearance was that of a small 
nebula, subtending an angle of three 
or four seconds, and of variable bright¬ 
ness. A luminous point would sud¬ 
denly appear in its centre, and as sud¬ 
denly disappear, and these changes 
would sometimes take place in the 
course of a few seconds. On the 5tli, 
6th, and /til, it was again observed, but 
not afterwards. The telescope was a 
Newtonian, of 6* inches aperture, with 
a power of seventy-four. 
NEW PATENTS AND MECHANICAL INVENTIONS. 
To W, F. Collard, of the Firm , Cle¬ 
ment!, Collard, and Co. Patent 
Piano Forte makers to the King , of 
Cheap side , London ; for New Patent 
Grand and Square Piano Fortes , with 
Harmonic Swell and Bridge of Rever¬ 
beration. 
T the suggestion of certain eminent 
musicians, a celebrated mathema¬ 
tician some years since directed his at¬ 
tention to enriching the tone of piano 
fortes by the aid of harmonics ; but his 
designs were never carried into effect. 
Clementi and Co., by their present pa¬ 
tent invention, obtain this desirable 
improvement, at the addition of a com¬ 
paratively trifling cost. 
By the i4 Bridges of Reverbe¬ 
ration,” the strings have the effect 
of being fixed, like those of the harp, to 
the sound-board itsel, finstead of being 
checked by an immediate attachment 
to a solid substance. This contrivance 
not only produces a more equal and 
rich flow of vibration, but takes away 
the whistling of the large steel strings, 
so common and often so disagreeable 
in grand piano fortes on the usual con¬ 
struction. It also gives the great ad¬ 
vantage of turning all those portions of 
the strings beyond the original bridge, 
which were before useless, to the aug¬ 
mentation and perfection of the tone 
produced on the main body of the in¬ 
strument, by means of the “ Harmo¬ 
nic Swell.” 
in expressive movements and legato 
passages the addition of the harmonics, 
independent of the beauty of sound, 
procures an advantage which must be 
obvious* 
