On Sun Pictures. 451 
paper, photographically prepared as before, the paper will be 
found to be very unequally darkened ;—at the chemical rays, 
represented by the colours blue, indigo, violet, lavender, and 
beyond that shade, the paper will be found to have the 
intensest black; at the lighting rays, shown by the colours 
yellow and orange, the paper will retain its primitive white- 
ness; and lastly, at the heating rays, to which the crimson 
belongs, the paper will be but slightly affected: the actinic 
power therefore seems also to belong, though in aminor degree, 
to the red and the crimson, representing heat—a circumstance 
which has not yet been satisfactorily explained. The light 
in Australia, therefore, is too yellow for the production of 
very quick pictures by any of the photographic processes ; 
but itis only a question of time, not of distinctness, upon 
that account. 
It is stated that the nearer we approach the equator, the 
more feeble become the chemical rays ; and consequently the 
more difficult are the pictures to be obtained. 
But, besides the chemical power being stronger or weaker 
in different latitudes, it is also found to be affected by the 
seasons and by the different times of the day ; thus the Spring 
and Autumn, and the early morning, are found to be the 
most favourable periods for the production of guick pictures. 
I shall now proceed to describe my method of preparing tho 
papers. 
PREPARATION OF THE NEGATIVE PAPER.—CHOICE OF 
PAPER. 
Whatman’s English paper is very good, but rather too 
thick for negative pictures, and hardly sufficiently well sized. 
for positives. 
Turner’s paper is good, but too expensive. 
