[53] In proceeding further on in Sir Henry’s volume, we have noticed an excellent observation quoted from Du Hamel: “The extension of the shoot is inversely as its induration, rapid while it remains herbaceous, but slow as it is converted into wood. Hence moisture and shade are the circumstances, of all others, the most favourable to elongation, because they prevent induration or retard it.” Although quoting this, Sir Henry recurs to his old opinions, and proceeds to observe, “Trees so circumstanced, push upward to the light; and from the warmth which their situation affords, their stems being thin and slender in proportion to their height, they are destitute of strength to resist the winds.” [54] We do not mention temperature, because we are not in possession of facts sufficient to lead us to form an opinion on the subject. Judging from animal analogy, of which our author is so fond, we notice, that those animals exposed in open atmosphere, have generally warmer blood than those who lurk in holes,—even than those of the same species who happen to live under shelter. Now evaporation takes place from animals as well as from vegetables, and the consequent cold is more than balanced by the heat of what may be termed the vital fire, which, like most other fires, burns brightest on exposure to a current of atmospheric air, being increased either by the result of the new chemical combinations having less capacity for heat, or by the stimulus of the fresh moving air exciting the vital action. Of the general influence of close forest on temperature, we are also not very well assured; but the few facts which observation has afforded, lead to the opinion, that to the northward of 50 deg. Lat. forests have higher temperature than bare country; that from about 50 to 30 degrees Lat. forests are cooler in winter and warmer in summer; and that nearer the equator, forests are generally cooler than bare country. But the temperature is regulated so much by the position of seas and lakes, in combination with the prevailing currents and strength of currents of the air—by the configuration of the country,—moisture and cloudiness of the atmosphere and quantity of rain,—by the composition, arrangement, and colour of the soil,—by the lower vegetable cover, and even by the nature of the forest itself, whether deciduous or evergreen, that particular facts must be very carefully weighed to enable us to reach general conclusions. It is generally understood, that forests render the climate moister.