GRIT 
the diftings pofition is difcoyered, the, upper part of the 
metal ai ee marked with a black ftroke, in order that it 
may always be lodged in the cell in the fame pofition, This 
is the caked Mr. Short always ufed; and the caution is fd 
fo much confequence, that he thought it neceflary to 
tion it very particularly in his printed directions for ay a 
of the iaftrument. 
And farther, Mr. Short frequently correéted the errors of 
the great by the little metal in another way, IF the great 
{peculum did not anfwer quite well in the hte ie he 
cured that defect, die YB by trying the effect of feveral 
metals faccefively, by this means correcting the errors of 
one by 
The ap Siete above-defcribed, for examining the para- 
bolic figure of the fpeculum, is rep refented in Pee V. Op- 
tics, fig. 7: A Ais ‘the mouth of the cise or edge of 
the great tube; B Bis a thin piece of w altened into 
and flufh with the end of the tube, to which is permanently 
fixed the annular piece of pafteboard f ¢, intended to cover 
and to prevent the a¢tion oP the correfpondin Be af the 
fpeculu m. D is an gaat piece gt of pallcbon by a 
pin to the Pires of wo hich it Tae: as ona 
centre ; fo that the wd Gnike nite ing H H may 
fhut up by the ring FF, or x She 8 ps Spee G G by the im- 
pectaeate piece E, in fuch that, in the firft inftance, 
reflection ma y be from a centre st in the latter, from 
a : cguane of the great fpeculu 
Mr. Mudge has remarked, that the daeaiiie of polifhing 
will not proceed well in the heat of fummer or the cold 
winter ; and that neither this, nor the other of grinding 
upon the the hones, will go on fo well, unlefs they be con- 
tinued uninterruptedly from beginning to end. In the above 
account it has been pitty that the metal to be mugen 3 
was about four inches diameter ; if it be either larger or 
fmaller, the fizes of the hones, Broiler, and polifher, mutt 
be propostnnab iy different 
procefs tor polifhing the little fpeculum of a tele- 
is no occafion for one in the a and likewife ae as 
the fpherical figure is the only object in this cafe to be at- 
tempted, the difficulty of execution is much lefs than in the 
former. As it is always neceffary to folder to the back of 
the little fpeculum a pice 4 brafs, as a fixture for the {crew 
to adjuft its axis; Mr. e has communicated a neat and 
method of doing it, ee he received from the late Mr. 
Jackfon, and which may be very ufeful to the optical or ma- 
thematical inftrument-maker upon other occafions. Having 
cleaned the parts to be eee 
tin-foil the exa& fize 
ftrong fo 
thon eee farfaces be ever 
- 
4 Newton had withed for, cor 
Braun which ret pe = a 
to Lele the fame with that 
of leaft five or fix inches diameter, i 
wood, 1 
obferving, that hod of 
t fpeculum y wasa. point 
_ee 
Goes not appear 
nian or Gregorian te- 
Mr. Short is faid to have poffeffed the fecret; how- 
ever, it died with that ingenious artift. The method difcover- 
ed by udge, above recited, is, as he has ftro 
of Mr. Short. 
this fubjec Smith's Optics, 
Mudge’s.excellent paper in the 
art. 16, p. 296—348. 
Grinpine is alfo ufed for a ei and lefs accurate me- 
thod of {moothing or polifhing the furface of 
cularly paubs for pace: lalfeg dee on : 
n the new method ag pi ay large plates of glafs for 
looking, coach-glaffes, 
uneven, it remains to be gro 
the plate of glafs is hid hot 
a table, and to fecure 
the machine ufed sheets 
cia 
mented to it ; ; aud aoa: this are proper weights a 
promote oe ‘gba the plank or P sabe en mene st ‘' 
wheel, which 
ives it motion. 
E or ben 
ued Bolithbes an and grows {moother, it SP igen 
time to time, and others put in its plac 
It is to be noted, > as guys the gel fize glaffes are thus 
the and fm 
ground witha mill; 
for the workmen to take hold of, and giveit scion What : 
remains ? 7 agaren) p ae comes under the denomi- 
prion re 
e Funica Nevia,... 
RINNAN, - Geography, one 2 fe Gallen Wy. 
y  GRINSRED, D Lewis. NY lat i: Whe long 7 ge. 
, Easr, a rome ; Rint 5 - 
rifh, in the hundred of Ruth ufhm see ot ha it and 
near the northern 
in qinie 
gat cats or moor-hen k aed 
and Hone parliament even fince irk ye 
1307. Thefe are eleéted by 36 bi 
Fela ie dis 
ount Si held i Se 
ae ee are held in this towa, thou , 
uke of Dorfet, built 
¢ 
refpeGtable charity Grin 
houfes, and i fahabisanth, thi cy 
_and on the great turnpike 
pg ano oO 
Here are three 
