270 Mr. Hunt on Light *mhich has permeated coloured Media^ 
The two papers A and G exhibit much more sensitive- 
ness to luminous influence than any others I have yet tried. 
8. The paper A, when w^ashed with a weak solution of 
the hydriodate of baryta, gives under the pencil of light a 
beautiful picture, whether used in the camera or for surface 
drawings. 
These pictures exhibit the peculiarities mentioned by Mr. 
Talbot at the British Association*. Sunshine changes ‘‘ the 
colour of the object delineated from reddish to black with 
great rapidity.’’ This gentleman adds, “ after which no 
further change occurs.” I much regret I have not been for- 
tunate enough to succeed thus far in fixing my drawings. 
The continued influence of light in a few months obliterates 
the impression. 
A singular change follows the exposures of these pictures 
to coloured light. 
If placed under vessels containing coloured fluids (4.) and 
exposed either to sunshine or to diffused light, in a few days 
the picture becomes a full red under the blue; a rose hue un- 
der the green ; a light blue under the yellow, and a deep blue 
under the red. These colours after deepening for some time 
gradually change to different shades of green under the blue 
and green fluids, to pink under the yellow, and a red \mdev 
the red fluid (25.). After this, the colours alter no more, and 
the picture bears exposure to light much better than at first; 
but I doubt if it is rendered perfectly permanent, for the dull 
light of January and February has spread a downiness, like a 
mist, over those photographs which have been constantly ex- 
posed. 
Daguerreotypes. 
9 . Exposing a plate, over which some lace was carefully 
placed, under four coloured glasses (2.) for three minutes to 
diffused light, I obtained, under the blue glass a beautiful 
copy ; no trace of a drawing beneath the green ; a tolerable 
impression beneath the yellow; but the mercury w’ould not 
attack the space beneath the red. 
10. A plate similarly arranged beneath four bottles of co- 
loured fluid (4.) exposed to diffused light for fifteen minutes, 
was found on being acted upon by the mercurial vapour to 
present the same appearance as above (9.), excepting that a 
faint design was evident over the space the carmine fluid had 
covered. 
11. I arranged a dark chamber, to which no other rays 
could pass but such as had permeated two inches of co- 
loured fluid. 
* Athenaeum, No. 618 . 
