On Sensible Temperature i 
139 
1830.3 
The latter is the general opinion, and that perspiration is the procedure by which 
the superfluous heat ns abstracted, and the temperature preserved at an invariable 
standard. The abstraction from the blood of a watery secretion, is said to absorb 
much heat, and the further conversion of that fluid into vapor greatly increases the 
effect. And we see that in estimating the full amount of the heat produced in the 
human body, reference must be had to this modification of its action. Now as we know 
that it would be exceedingly difficult to estimate the amount of the heat disposed of 
in this way, our object should be to consider that particular limit of the question - 
where we may be certain that all the excess of heat generated in the body is car- 
ried off by the contact of the medium, and that, consequently, there is an equili- 
brium between the heat generated every instant in the body, and that carried off 
by the conducting powers of the medium. To ascertain what this particular con- 
dition of things may be, requires, however, some previous observations as to the 
state of our feelings, under different circumstances of temperature and of medium. 
But as our feelings are fallacious guides, when we wish to compare the intensity of 
the cause acting on them, it were to be wished, in order to prosecute the inquiry 
with that precision which the subject demands, that some method were devised of 
measuring our sensations, or to speak more correctly, of measuring some parallel 
phenomenon, that we maybe certain will, in its relative amount, afford an exact idea 
of the energy of the exciting cause on which our sensations depend. No such 
scale has as yet been applied to determine the comparability of our sensations as to 
heat or cold ; and it is perhaps to the want of some such means of accurately esti- 
mating them, that we are to attribute the little progress made in the subject of ani- 
mal heat. 
Nor is it easy to devise any such scale. So as to be universally applicable, and 
yet accurate in its indications. I have, at least fora considerable time past, sought 
some method of the kind, and have not as yet fully satisfied myself on the sub- 
ject. Some conclusions of interest, however, I have arrived at, I think : and as the 
little 1 have done may afford hints to others, who may be more fortunate than I 
have been ; and as it may at least stimulate those who have sufficient leisure (which 
I am sorry to say is not my case) to multiply even the imperfect observations 1 
have had recourse to, I shall endeavour here to give some account of them. 
The general introduction of the thermometer into our houses has made ordinary 
people, however unaccustomed to observe and to compare, sensible of its inade- 
quacy, as a guide to the feeling we have of varying temperature. It is a common 
remark, how fallacious an index the height of the thermometer is to the conclu- 
sion we shall form as to the weather being warm, or temperate , or cold — at least 
within certain limits. Everyone who has experienced our hot winds in the north- 
western provinces, knows that, even with the thermometer at 100°, the feelings are 
less oppressed than they are in other parts of the country or other seasons of the 
year, with the thermometer at 86*. This truth is so commonly acknowledged, viz. 
that a difference of 10*, or even more in temperature may occur, and yet the very 
reverse terms be applied, which the order of the numbers would authorise, that it is 
unnecessary to dilate further on the subject. 
The reason of this will be evident to those who consider what is the nature of the 
information which the thermometer gives us, and what is the information we are 
seeking. The thermometer merely gives us the temperature of the medium in 
which we are immersed, but temperature is only one of the many circumstances 
which affect rapidity of cooling, — the real question we are enquiring into. For, con- 
sidering the animal machine as a continual generator of heat, the question is, Un- 
der what circumstances is this heat, which would otherwise continually accumulate, 
carriedoffor dissipated in the most rapid or effectual manner, and vice vend? 
The former will be coldest to our feelings, the latter warmest. Now with regard 
to the cooling of bodies, the following circumstances are found to affect that pro- 
cess universally. 1. Difference of temperature ; 2. Specific beat of the medium ; 
3. Conducting power of the medium; 4. Quantity of the medium applied to the 
cooling body; 5. State of the surface as to evaporation. It is necessary to esti- 
mate the effect of each of these circumstances; while the thermometer, as usually 
employed, merely gives information regarding one of them. 
But there is a method of using the thermometer, that enables us to answer most 
of these questions, if not all : and it is the object of the present paper to explain it, 
and to indicate some of the results which the writer has obtained. It is evident, 
if a thermometer be heated to the temperature of the blood, and be then expos- 
ed to the cooling powers of the air ; that the direct effect of all these circumstances, 
except the last, will be indicated by the rapidity with which it loses its excess of 
