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amount of exposure appeared to produce an image. It is 
not likely , therefore, that, for years before (the mechanical 
production of pictures was in full operation in 1790), his 
intimate friend Matthew Boulton should not only have been 
in possession of a secret mode of fixing images of pictures 
but actually producing and selling large numbers of them. 
For this and other reasons we must, I think, decide that these 
pictures could not in any way have been produced in the 
camera; besides the great size and the perfect definition 
would be beyond the power of any instruments that could 
then be made. There is another argument, too — that if the 
camera could have been used, paintings would have not been 
the only subjects reproduced — views from nature, or, at any 
rate, works of art, would have been experimented upon. 
On some of the pictures are seen curious small spots, each 
casting a shadow in the same direction — a very familiar 
appearance to those who have copied oil paintings in a raking 
light, when each raised spot of colour does actually cast its 
shadow. This has been considered an evidence of the pic- 
tures having been produced by the camera; but I shall 
further on be able to account for this appearance in another 
way. 
Although we cannot call these pictures photographs, seeing 
that they have been produced by some different process from 
any we are acquainted Avith, we have the distinct evidence of 
Dr. Lee and Mr. Hodgson, clear and unmistakeable, that 
pictures produced by this mechanical process were pointed 
out by Matthew Boulton as having been produced in some 
way by sunlight. 
Perhaps Ave shall do Avell to narroAv the field of inquiry, by 
considering some of the suggestions that have been made, 
and shoAving Iioav they could not have been produced. 
We may decide that they could not be copies by hand: — 
1st. Because they are distinctly called ££ mechanical pictures,” 
produced by a secret process. 2nd. Because in two copies of 
