able combination of chemicals,
consisting of a mixture of iodine, bromine, iodus, and iodic acid, and
a proper combination of those bodies gave an action somewhat more
sensitive than chloride of iodine--but the "high lights" of the
portraits would become solarized or overdone, more frequently with this
combination than with the chloride of iodine. Throughout the year
1841, I used, with great success, chloride of iodine, applied as one
coating--occasionally in conjunction with Mr. Wolcott, attempting the
use of iodine, bromine, and chlorine, and at times with more or less
success. The difficulty of exactly combining, the three elements above
mentioned, in order to produce a certainty of result with harmony of
effect, was the work of many months, with great labor and study, the
slightest modification requiring a long, series of practical
experiments, a single change consuming, frequently, an entire day in
instituting comparisons, etc., etc.

Early in the year, 1842, I discovered a combination of chemicals (now
known in London as "Wolcott's Mixture," in hermetically sealed bulbs)
of exceeding uniform character, very sensitive to the action of light,
and specimens produced in 1842-3, with this combination, will bear
comparison with the best specimens produced at this late date.

About the same time, I discovered that however much overdone a
Daguerreotype might be, the means were at hand to save or redeem it.
It has long, since been known to operators, that if a plate be exposed
to light after being coated, unless it be again coated, a clear and
distinct picture could not be obtained upon the same plate without
first repolishing and recoating the same, care being taken that no
light fall upon the prepared surface. To prevent solarization, coat a
plate as usual, expose to the action of light any required time
(according to circumstances), say from quarter to one half more time
than would be required in the ordinary method of procedure; observe,
before putting the plate in the mercury box, place it over the vapor of
iodine, bromine, or chlorine, etc. (carefully excluding the light),
for a very brief period, great care being required to have the selected
vapor very much diluted with air, in order to success. Many
experiments will be required ere arriving at satisfactory results.
Specimens now unknown to general operators, for harmony of effect, have
been, and may again be produced by the method pointed out above. I
have