The Micrcfcope explained. xvii 
Diredl: your inftrument to any external objects and 
if your room is a little darkened, you will have an ex¬ 
tremely vivid and beautiful picture upon the grey glafs 
at rq fig. 9. But inverted, the outlines may be nice¬ 
ly traced with a black-lead pencil upon the glafs, which 
being taken out and covered with a paper and held 
againft the light, may be nicely copied, and afterwards 
fhaded by the picture upon the glafs, when put into its 
place, the black lead lines being firft wiped off, with 
the corner of a napkin a little wet. 
Note, this fecond form of the camera obfcura hath 
the following advantages ; firft, as the picture is formed 
immediately, by the rays palling thro’ the convex lens 
without any reflection, the objects are extremely vivid ; 
and although the outlines muft be traced in its inverted 
ftate, yet when the glafs is taken out and turned the 
other edge downward, every part of the picture will have 
its proper attitude. 
Secondly, a very great advantage arifes from this ap-' 
plication of the inftrument, in diminifhing large draw¬ 
ings or paintings to a fmaller fize, viz. Set the ori¬ 
ginal painting upon a chair againft the wall, but topfide 
turvy, and you will have a lively reprefentation of it 
upon the grey glafs in an eredt polition ; and if the room, 
be long enough, a whole length pidture may be taken in, 
and the reprefentation may be either larger or fmaller, as 
you either remove the inftrument, or pidfure, farther 
from or nearer to each other; the change of the convex 
lens wdl do the fame thing. When this operation is 
performed, the pidfure to be copied fhould be placed near 
a window, and you fhould fit with the inftrument, next 
a remote window, and fliut the fhutter of that or thofe 
windows which are behind you, to exclude the light as 
much as poftible, from falling upon the grey glafs q r. 
ft hirdly, portraits may be corredlly out-lined in this 
pofitipn of the inftrument j and the greateft pofnble like— 
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