e is a further reason: the scientific
discoverer must speak of the apparatus by which he experiments, and mine
was often my own physical frame.

Twenty years ago, while yet my mind, laboring with this great subject,
was condemned

"to drudge
Without a second and without a judge,"

you, sir, comprehended the hypothesis which has now become a theory, and
you waited not for others to speak, but you fully acknowledged its
truth; and although, in Hartford, as now in New-York, you were thronged
with practice, (then allopathic), you yet found time to furnish me with
added experiments, made in your office, confirmatory of its truth, which
by your permission were afterwards added in your name to my published
work.

The first step in the theory occurred to my mind in the winter of 1822,
and while I was engaged in founding the Troy Female Seminary. Being in
attendance on a course of lectures on chemistry, and at the same time
teaching to a class Mrs. Marcett's excellent work on that subject, one
cold morning, as I was walking briskly up a hill, I said to myself, Why
do I grow warm? Whence comes this accession of caloric? It cannot be
transmitted to me from any object without, because every thing which
comes in contact with me is cold. Snow is under my feet, and frosty air
surrounds me; and, as to clothing, even the softest furs _impart_ no
warmth--they but keep from escaping that which comes from within. What
other method besides transmission is there of gaining heat? There is the
elimination of caloric, when, in substances chemically combining, weight
is gained and bulk is lost. Is there any such combination going on in
me? Yes; this atmospheric air, when I inspire it, has oxygen combined
with nitrogen; but when I expire, the oxygen has disappeared, and
heavier substances--carbonic acid gas and watery vapor--are returned in
its place. Thus, it must be, animal heat is evolved. It is the product
of respiration; and it is because I breathe faster and deeper, that more
carbon is oxidized or burned, and more heat is set free in my lungs; and
therefore I grow warm as I walk up this hill, though all around me is
cold.

The mind, excited by new and great thoughts, works with unwonted energy;
and mine at once collected so many proofs, that I became perfectly
convinced of the truth of the hypothesis. In searching books, I found
that Lavoisier had taught the same; but he dying, his doctrine was
dis