Still, we are not altogether ignorant; some circumstances appear to be followed by effects so definite, that we may almost consider we have before us, in true position, cause and effect.  Let us look at this position in reference to the simple influence of temperature on the value of life.

If we observe the fluctuation of the thermometer by the side of the mortality of the nation at large, no calculable relationship seems, at first sight, to be traceable between the one and the other.  But if, in connection with the mortality, care be taken to isolate cases, and to divide them into groups according to the ages of those who die, a singular and significant series of facts follow, which show that after a given age a sudden decline of the temperature influences mortality by what may be considered a definite law.  The law is, that variations of temperature exert no marked influence on the mortality of the population under the age of thirty years; but after the age of thirty is reached, a fall of temperature, sufficient to cause an increased number of deaths, acts in a regular manner, as it may be said, in waves or lines of intensity, according to the ages of the people.  If we make these lines nine years long, we discover that they double in effect at each successive point.  Thus, if the, fall in the temperature be sufficient to increase the mortality at the rate of one person of the age of thirty, the increase will run as follows:  1 death at 30 years of age will become 2 deaths at 39 years of age, 4 at 48 years, 8 at 57 years, 16 at 66 years, 33 at 75 years, and 64 at 84 years.

In these calculations nothing seems to be wanting that should render them trustworthy; they resulted from inquiries conducted on the largest scale; they were computed by one of our greatest authorities in vital statistics, the late Dr. William Farr, and they accord with what we gather from common daily observation.  They supply, in a word, the scientific details and refinements of a rough estimate founded on universal experience, and they lead us to think very gravely on many subjects which may not have occurred to us before, and which are as curious as they are important.

We often hear persons who know little about vital phenomena, by which term I mean nothing mysterious, but simply the physics embraced in those phenomena which we connect with form and motion under the term life, harping on the one string, that man knows nothing of the laws of life and death.  But what an answer to such presumption do the facts rendered above supply.  Life and death are here reduced, on given conditions, to reasonings as clear and positive as are the reasonings on the development of heat by the combustion of fuel.  It is not necessary for the vital philosopher to go out into the towns and villages to take a new census of deaths to enable him to give us his readings of the general mortality under the conditions specified.  He may sit in his cabinet, and, as he reads his thermometer