DEL 
fliding the point up or down in the groove in blade of 
the fquare, it will,be brought to cover the obje&; he then 
marks the point m, and Gndsanother in the ae manner ; 
when points are thus found, it will be eafy to conne& them 
by lines, and thus complete the outline ; the point at m fhould 
13 to throw it 
""TrantaStions. 
saa it sae 
in hick the two (seas inftruments may : fupported. 
Figs and 3, are reprefentations . a de elineator de- 
fcribed i in nie een uae Journal, vol. by ir, R. 
ria Bdge- 
as to fig. 3, by oe aie board a tothe drawing 
board, and by putting one end of the paper under the board 
a, it will be fixe wa s the fight, capable of being ele- 
vated or depreifed a esas requires: in ufing the inftru- 
‘ment the a looks brongh the fight, the boards being 
Jaid out flat and directs the point of the index 
1 m, to interfee fae pee he "oie to delineate ; he then 
doubles up the machine a3 in fg. 3, bringing the index upon 
the paper, but taking care not to move the index with re- 
{pe& to itfelf; he then marks the place en the point of 
the index lies, and makes another obfervation ; having thus 
obtained phi oe points, he proceeds to draw the lines and 
finifh the ou 
The camera ner is frequently ufed as a delineator, for a 
defcription of which fee that article ; though the fize which 
this inftrument muft have to an{wer the purpofe effeCtually, is 
an objeCtion to it, which, however, applies to all the ma- 
chines we have hitherto defcribed. nf optigraphs spots 
» poffeffes 
lum ¢, 2 8 
E. 
ly eafy, eihou t hake, in the tu ed is fo 
contrived as to sede all the freedom “of a a when held in 
the hand for 
“5p concleat a fe&tion of the telefcope, being the 
principal part of the invention. 
coming to the plane mirror E, are reflected i 
{cope, pafling irene: the obje& glafs 3, aa: placings the 
Speculum a are reflected cough the eye-glals d, to the eye 
DEL 
ate; fisa piece of parallel g'afs, with a a dot on its 
ae exaétly in the focus of the eye-glafs. - 
ae fs ufing the cae 
o be e an 
your left hand alter the peau of Ee mirror E, until the 
5, is on fome particular part 
obje& that you wifh t to ) begin with, adjufting the te. 
Icleope to diftin@ vifion by the milled head P. Then by 
moving your hand (having the pencil), you pafs the dot feen 
in the field of the telefcope over the objeét, the pencil mark- 
a it at the fame time on the paper. 
make ae drawing larger, pull out the tube of the 
and fix it wit th the fcrew e ; then ull out 
and 6 Lane 
next a linesor we fhall defcribe is the camera lucida, 
fanented by Mr. W. H. Wollafton, and for which he took 
out a patent in 18063 for portability this exceeds all ii 
inftruments for the fame purpofe. It is reprefented in fig. 6, . 
which only explains the ftand or fupport for the initre ment ; ; 
its i ae is explained by fig. 7; a4 de, isa fection of a 
ae when in ufe is fixed with the fide ad towards 
the aera to be delineated, and the eye at the angle e; the 
rays from the objects enter at the fide ad, and falling upon 
b are refleGted by it to de, and from thence to the eye at ey 
entering it in a haga Lal eared to what they came 
to the prifm ; in this manner a picture 0 whatever is before 
the fide ad is fie won the furface ed; now to tranf- 
e eye is fo laced at e, that one 
half of th a 8 
while the other half fees (by dire& vifion clear of the fide e d 
of the ely the paper placed on a table beneath the prifm 
at fg; a pencil or pen may be traced over this paper, 
and rill appear to the eye as though it was traced over the 
refleted image. This prifm is mounted in a brafs li 
leaving open fuch places as are neceflary as feen in fg. 6; 
pin 4 is fix ed to the cafe of the prifm, and ae t fish a 
piece of brafs jointed to a tube, 2, This tube flides up and 
down within another, 4, which is fixed by a ey to a clamps, 
: {crewed to the table whereon the paper is lai id~ 
tion, fo as to throw the image 
paper. 8 ce principle of the inftrument depends upon 
© feeing the reflected images of the objects, and the dire& 
vifion of the os at the fame time, the leafk motion of 
ould caufe it to fee either the refleQed 
only the pencil and 
paper at fg 3 to prevent this, a piece of brafs plate, n, fig. 65 
is fxed on by a fcrew, roun which it turns as a centre ; it 
a 
pw 
ther 
brafs fight fhou prifm, 
Thofe perfons whofe = is not quite perfeét, will not 
fee 
