158 
It has been stated on good authority, I believe, that a 
darkened room or tent was used, also that the presence of 
sunlight was required in the process. Now this at once sug- 
gests the use of the camera obscura — an instrument which 
was perfectly well known at that period. A common method 
of exhibiting this instrument was to darken a room and fix 
a lens in a hole made in the window-shutter, and view the 
images produced on a screen of paper placed opposite to the 
lens. By this method a reversed and inverted picture would 
be seen by the spectator. 
Another form of camera in use at that time consisted of an 
upright box with a sliding tube through the top, in which 
was fixed a lens, and above this a mirror placed at the 
angle of 45°. This form is still in use for the purpose of tracing 
images thrown on to paper placed at the bottom of the box. 
These primitive forms of the camera must be well known to 
all present. I name them only as affording some explanation 
for the use of the darkened room or tent. 
The next question which suggests itself is this : — Did they 
employ the camera in producing images on chemically pre- 
pared surfaces ? In fact, did they practice what we now 
name photography ? 
It is stated that in 1802 Wedgwood and Davy experi- 
mented with salts of silver on leather, and produced impres- 
sions of various objects. Now if we may be allowed to 
imagine that Mr. Boulton and his colleagues were acquainted 
with this effect of light on such substances, they might have 
reasoned on the phenomena, and prepared paper with these 
constituents — tannic acid, gelatine, and some salt of silver. 
Had they done so they might have produced a picture by 
sufficient exposure in the camera. One thing is certain, the 
pictures 7 and 8 have a plentiful coating of gelatine, albu- 
men, or some other substance on their surface * 
* Mj son William Dancer tested this substance and pronounced it to be 
gum. 
