XV 
<?he Mi cr of cope explained. 
ble acquisition of having it in our power to keep draw¬ 
ings of thofe beautiful appearances, which require no 
more trouble, than that of tracing the lines with a pen 
or pencil. 
* 
The ufe of the pyramidical camera obfcura, in 
defigning and taking perfpedive views. 
A CAMERA obfcura, is any dark place, wherein 
objects expofed to broad day light are reprefented 
upon paper, or any other proper white body, in their 
true proportions, with all the livelinefs of colours, and 
diverfity of motions, amazingly pleafant to behold. The 
advantages arifing from the ufe of this inftrument, to 
draft’s-men in general, are fo great and fo well known, as 
to need no enumeration. Therefore we (hall only add, 
that it is of very great ufe in giving the proportionable 
hze of every feparate object, or feparate groups of ob¬ 
jects in the fame picture; by which means they may be 
copied after nature in the moft perfedf manner, and 
that conftant difficulty removed, which requires fomuch 
time and ftudy to give the feveral objects their true big- 
nefs and proper fituation in the picture from the fame 
point of fight. 
There are two double convex lenfes in fquare ma¬ 
hogany frames ; one of which is to be ufed for diftant, 
the other for near objects. They are to be put into the 
fquare Aiding tube P Q, fig. 8. at d under the mirror r, 
their foci is marked upon each frame. 
The pyramidical form of this inftrument is allowed by 
a number of gentlemen who have experienced its utility, 
to be fuperior to thofe of any other conftrudtion hitherto 
made, having every deftred advantage to exclude the 
light, and when you have done with it at any time, it 
is readily put up into a portable fize. 
Fig. 8. 
