his appearance, I conjectured
that these bordering portions might have absorbed a lesser quantity of
salt, and that, for some reason or other, this had made them more
sensitive to the light. This idea was easily put to the test of
experiment. A sheet of paper was moistened with a much weaker solution of
salt than usual, and when dry, it was washed with nitrate of silver. This
paper, when exposed to the sunshine, immediately manifested a far greater
degree of sensitiveness than I had witnessed before, the whole of its
surface turning black uniformly and rapidly: establishing at once and
beyond all question the important fact, that a lesser quantity of salt
produced a greater effect. And, as this circumstance was unexpected, it
afforded a simple explanation of the cause why previous inquirers had
missed this important result, in their experiments on chloride of silver,
namely, because they had always operated with wrong proportions of salt
and silver, using plenty of salt in order to produce a perfect chloride,
whereas what was required (it was now manifest) was, to have a deficiency
of salt, in order to produce an imperfect chloride, or (perhaps it should
be called) a _subchloride_ of silver.

So far was a free use or abundance of salt from promoting the action of
light on the paper, that on the contrary it greatly weakened and almost
destroyed it: so much so, that a bath of salt water was used subsequently
as a fixing process to prevent the further action of light upon sensitive
paper.

This process, of the formation of a subchloride by the use of a very weak
solution of salt, having been discovered in the spring of 1834, no
difficulty was found in obtaining distinct and very pleasing images of
such things as leaves, lace, and other flat objects of complicated forms
and outlines, by exposing them to the light of the sun.

The paper being well dried, the leaves, &c. were spread upon it, and
covered with a glass pressed down tightly, and then placed in the
sunshine; and when the paper grew dark, the whole was carried into the
shade, and the objects being removed from off the paper, were found to
have left their images very perfectly and beautifully impressed or
delineated upon it.

But when the sensitive paper was placed in the focus of a Camera Obscura
and directed to any object, as a building for instance, during a moderate
space of time, as an hour or two, the effect produced upon the paper was
not strong enoug