1804. | 
oue beam, one end pulling the middle 
of that in the former row, and the 
other end pulling the middle of the 
remaining beam in the fecond row. 
This tat beam having eight flrings to 
pull at one end, and only four at the 
other, muft not have its knife-edge in the 
centre, but the diftance between the edges 
at each end mult be divided into three 
equal parts, and the edge of one placed 
at the diftance of one part from the edge 
of the other. By this means the tenfion 
will be equally diftributed through the 
twelve Arings. While ali the tenfions re- 
main dependent on each other, and detach- 
ed from every thing elfe; any laxity of 
one ftring will be communicated to the 
re(t. Suppofe, for inftance, the fring on 
the firlt beam relax 4th of an irth; the 
end of the beam behind it wou.d move 
back 4th of an inch; the end next behird 
that, would move back 3th, and that 
behind in the fourth row 5d of an inch; 
an equal tenfion being {till preferved 
through all the ftrings. To diminihh fric- 
tion, the beam fhould be at right angles 
with the ftrings, 
The beams may be made of two thin 
pieces of brafs, with the knife edges 
between; and thefe may anfwer the pur- 
pole of ivets by fixing the fides parallel 
_ to one another; or the beams may be one 
folid piece of brafs, with the knife-edges 
projecting on each fide. The fteel of 
which the edges are made muft be hard, 
and thote of different. beams may be con- 
nected by a piece of fteel wire, in the fhape 
of an S, or flat with a hole at each end. 
In making choice of the catguts care 
fhould be taken to get them as nearly as 
poflible of one thicknefs, and this diame- 
ter fhou'd be meafured by a feétor of the 
fame kind as thofe made u‘e of to meafure 
wires, but of greater length and accuracy, 
and fteel edges are preferable. By the 
fector made ule of by the Patentee, we are 
told he can meafure wire to the xobooth 
part of an inch; if catgut twitea with 
wire be thought defirable, the proper fize 
will be eafily found by a few trialsof thofe 
of different thickneffes. 
The bridges may be varioufly confruét- 
ed, but the following method is recom- 
mended by Mr. Wood : 
Juft before the machinery fix one bridge 
of hard wood, or any fuitable fubftance, 
Jong enough to fupport all the ftrings, 
‘Lhis muft be Jevel with the firings, from 
each end, and from the middle of the 
bridge muft projeét, a firmly fixed pin, 
with a {crew at the top, paling through 
a piece of wooed above, fimilar to the. bridge 
New Patents lately enrolled. 
235 
below. The edges muft be fo formed 
that when preffed together, they may 
touch every ftring, and a thin fmooth 
piece of leather glued to one fide may be 
tound an advantage. On the ferew of each 
pin mut be anut, to prefs the two bridges 
together. 
At the other end of the inftrument each 
fring mut have a bridge, with a notch at 
the middie to keep it fteady, hollowed a 
little underneath, and made rough to pre- 
vent its flipping. Having given a proper 
tenfion to the whole, the ftrines muk be 
brought in uniion by varying their lengths, 
moving each bridge feparately by the 
fingers or a forceps. During the opera- 
tion of tuning, the upper bridge mult not 
be fcrewed, but only preffed with the hand 
againft the other whenever the vibration 
of the ftring fhail be tried. The inftru- 
ment being tuned, the bridges are to be 
{crewed together, and the infliument is - 
ready for ufe. Whenever it is out of tune, 
feparate the bridges, to Jet the ftrings 
and machinery play freely; again fix the 
bridge, and the inttrument, if accurately 
made, and if the relaxation is not exceed- 
ingly great, will be again to tune. 
The patentee next defcribes how his 
invention isapplicable to the {quare piano- 
forte, both with and wthout addi:ional 
keys. He then gives rues and calcula- 
tions with regard to the lengths and dia- 
meters of the ftrings, and ve adds, that, 
‘6 the application is fo perieftly new, and 
in fome few parts apparently complex, 
though in itfeli fimple, that I am afraid 
it will occafion confiderable time and trou- 
ble, even to one converfant in the bufis 
ne{s, before he be able in every refpect 
to comprehend my defcription. Many of 
the calculations will be troublefome, but 
I have explained them as well as I 
could, and have alfo made references, 
by attending to which, the reader may 
learn more on the fubject. 
In moft queftions refpeéting vibrations, 
and particularly where the tenfion varies, 
Joganthms will be found of great affif- 
tance.” 
MR. JOHN PORTER’S (LEMONVILLE, 
IRELAND) for a@ LAMP 0” a new 
CONSTRUCTION, 4 
The diftinguifning charaéteritic of this 
lamp is, that it is fufpended on an axis, 
on which it moves while burning. On the 
fide of this axis which is oppofite to the 
burner, the lamp conains the greareft 
part of the oil or fpirits, and on the other 
fide is placed fo much metal or other fub- 
ftance, as makes the lamp hang level, 
Liz cr 
