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 This combustion is rapid, or slow, in proportion saas [sic] the air around the body is colder, or warmer than the independent temperature of the body.

An excessively rapid, or slow combustion, are alike unfavorable to the physical development of the human frame. In a climate where the air is at the temperature of zero, there is a differance of 98° between the heat of the air and that of the human body exposed to it: and, in order that man may live in such climate, he must develope a very large quantity of heat by proportionate rapidity of combustion in his lungs. In order to support such combustion, the blood must be furnished with a large proportion of carbon; the food must be large in quantity and coarse and oily in quality: even then, so much of the blood is consumed in respiration, that too little is left for the full development of the human frame: hence the huge appetites and small stature of the hyperborean races.

Hence also, an excessively cold climate, by arresting the full development of the human frame, also arrests the full development of the physical strength in man, an element necessary to civilization. Other facts must be taken into the account. M. Quetelet has shown that the power of the human frame to resist cold, is greatest, at the age of 17 years: after which age, the frame is less and less able to endure an extremely cold temperature. The same writer has demonstrated, that in man the maximum of physical strength (and of the passions) occurs at 25 years of age; whilst the maximum of intellectual power does not occur until after the 30th and 35th year of age.

From these facts it follows that a people, advancing in civilization, require to be in force, in other words, require a large proportion of their number to be in full health and development at 25 years of age, for physical strength; and a large proportion in full development at from 35 to 40 years of age for intellectual power.

In extremely cold climates, the mass of the population are cut off before reaching twenty-five years of age—and hence do not reach the maximum of physical nor intellectual power. And those who do reach these maxima, having already passed the age when they best endure rigor of climate, are more and more depressed by this last element, which they are less able to bear up against, every year they reach beyond seventeen. Besides, this imperfect development occurs in a region where nature offers the most formidable physical barriers to civilization. And these facts, together, afford ample reason why excessively cold climates have not been the centres from which have radiated human civilization.

In extremely cold climates, the independent heat of the human body is maintained by a rapid combustion, or consumption of the particles of which the body is composed (all which particles are held in solution by the venous blood as it passes through the lungs :) and this rapid combustion is owing to the necessity of maintaining the independent heat of the body, when there is a great difference between that heat, and the temperature of the surrounding air. Starting from this great difference, we arrive at a point in temperature or climate, where there is less difference between the climate temperature and the independent heat of the human body; here, the combustion will be slower, the consumption of particles less rapid, and the development of physical power will also be relatively greater. Keeping on in the same direction we arrive at another point in temperature, which exactly coincides with the independent heat of the human body. In this last instance combustion (by