During the month of April in the year 1855, the following letter 
appeared in the pages of "The Photographic and Fine Art Journal" (April 
1855) pages 124-125:
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      DAGUERREOTYPING ON THE ROCKY MOUNTAINS.
                                       New York, March, 20 1855.
 
To H. H. SNELLING ESQ.

   DEAR SIR:--I am very sorry I am unable to respond to your request 
for the particulars of my tour with Colonel J. C. Fremont, in his late 
Exploring Expedition across the mountains, not having taken any private 
notes.  But this much I am at liberty to say that I succeeded beyond my 
utmost expectations in producing good results and effects by the 
Daguerreotype process, on the summits of the highest peaks of the Rocky 
Mountains, with the thermometer at times from 20 to 30¡ below zero, 
often standing to my waist in snow, buffing, coating, and 
mercurializing plates in the open air.--In nearly every instance 
Barometrical, and Thermometrical observations were obtained at the same 
moment, with the picture.  The time given to each example was also 
noticed and marked on the plate.  I requested permission from Col. 
Fremont who readily afforded the means to make these observations, and 
they may account for the very great difference of time, which it took 
to make pictures, under apparently the same combination of 
circumstances.  All these observations have been carefully noted and 
will be published for the benefit of the scientific world, in Col. 
Fremont's forthcoming Journal, which these pictures will serve in some 
measure to illustrate.
   I had considerable trouble with the iodine, which under ordinary 
circumstances requires 80¡ Fht. before it will part with its fumes.  I 
had to use artificial heat in every instance, I found it necessary to 
make up in quantity for the loss of temperature.  I generally employed 
Anthony's Anhydrous sensitive, and my boxes during a continual use of 
five months only required replenishing four time, notwithstanding they 
were opened every time I made a picture, to arrange it smoothly at the 
bottom.  The coating boxes were made expressly for my use on the 
Expedition by E. Anthony Esq. And I cheerfully recommend the use of 
similar ones for like purposes.  Notwithstanding the earnest 
prognostications of yourself and my professionals friends, both in New 
York and Philadelphia, that under the difficulties I was likely to 
encounter on the snow capped mountains,--I would fail, I am happy to 
state that I found no such word in my vocabulary although I had not 
much youthful, or physical strength to bring into the scale.

                              I am Dear Sir yours truly.
                                            S. N. CARVALHO.


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Posted for your enjoyment.     Gary W. Ewer     
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04-22-99