To many creatures there is in this sense but one necessary of life, Food. To the bison of the prairie it is a few inches of palatable grass, with water to drink; unless he seeks the Shelter of the forest or the mountain's shadow. None of the brute creation requires more than Food and Shelter. The necessaries of life for man in this climate may, accurately enough, be distributed under the several heads of Food, Shelter, Clothing, and Fuel; for not till we have secured these are we prepared to entertain the true problems of life with freedom and a prospect of success. Man has invented, not only houses, but clothes and cooked food; and possibly from the accidental discovery of the warmth of fire, and the consequent use of it, at first a luxury, arose the present necessity to sit by it. We observe cats and dogs acquiring the same second nature. By proper Shelter and Clothing we legitimately retain our own internal heat; but with an excess of these, or of Fuel, that is, with an external heat greater than our own internal, may not cookery properly be said to begin? Darwin, the naturalist, says of the inhabitants of Tierra del Fuego, that while his own party, who were well clothed and sitting close to a fire, were far from too warm, these naked savages, who were farther off, were observed, to his great surprise, "to be streaming with perspiration at undergoing such a roasting." So, we are told, the New Hollander goes naked with impunity, while the European shivers in his clothes. Is it impossible to combine the hardiness of these savages with the intellectualness of the civilized man? According to Liebig, man's body is a stove, and food the fuel which keeps up the internal combustion in the lungs. In cold weather we eat more, in warm less. The animal heat is the result of a slow combustion, and disease and death take place when this is too rapid; or for want of fuel, or from some defect in the draught, the fire goes out. Of course the vital heat is not to be confounded with fire; but so much for analogy. It appears, therefore, from the above list, that the expression, animal life, is nearly synonymous with the expression, animal heat; for while Food may be regarded as the Fuel which keeps up the fire within us -- and Fuel serves only to prepare that Food or to increase the warmth of our bodies by addition from without -- Shelter and Clothing also serve only to retain the heat thus generated and absorbed. The grand necessity, then, for our bodies, is to keep warm, to keep the vital heat in us. What pains we accordingly take, not only with our Food, and Clothing, and Shelter, but with our beds, which are our night-clothes, robbing the nests and breasts of birds to prepare this shelter within a shelter, as the mole has its bed of grass and leaves at the end of its burrow! The poor man is wont to complain that this is a cold world; and to cold, no less physical than social, we refer directly a great part of our ails. The summer, in some climates, makes possible to man a sort of Elysian life. Fuel, except to cook his Food, is then unnecessary; the sun is his fire, and many of the fruits are sufficiently cooked by its rays; while Food generally is more various, and more easily obtained, and Clothing and Shelter are wholly or half unnecessary. At the present day, and in this country, as I find by my own experience, a few implements, a knife, an axe, a spade, a wheelbarrow, etc.