The fact that we use the digestive and nutrient apparatus of sheep, oxen, &c., for the preparation of our food, is merely a transitory barbarism, to be ultimately superseded when my present subject is sufficiently understood and applied to enable us to prepare the constituents of the vegetable kingdom in such a manner that they shall be as easily assimilated as the prepared grass which we call beef and mutton, and which we now use only on account of our ignorance of the subject treated in the following chapters. I do not presume to assert or suggest that my efforts towards the removal of this ignorance will transport us at once into a vegetarian millennium, but if they only open the gate and show us that there is a road on which we may travel towards great improvements in the preparation of our food as regards flavour, economy, and wholesomeness, my reasonable readers will not be disappointed. So much of cookery being effected by the application of heat, a sketch of the general laws of heat might be included in this introductory chapter, but for the necessary extent of the subject. I omit it without compunction, having already written ‘A Simple Treatise on Heat,’ which is divested of technical difficulties by presenting simply the phenomena and laws of Nature without any artificial scholastic complications. Messrs. Chatto & Windus have brought out this little essay in a cheap form, and, in spite of the risk of being accused of puffing my own wares, I recommend its perusal to those who are earnestly studying the whole philosophy of cookery. CHAPTER II. THE BOILING OF WATER. AS this is one of the most rudimentary of the operations of cookery, and the most frequently performed, it naturally takes a first place in treating the subject. Water is boiled in the kitchen for two distinct purposes: 1st, for the cooking of itself; 2nd, for the cooking of other things. A dissertation on the difference between raw water and cooked water may appear pedantic, but, as I shall presently show, it is considerable, very practical, and important. The best way to study any physical subject is to examine it experimentally, but this is not always possible with everyday means. In this case, however, there is no difficulty. Take a thin[1] glass vessel, such as a flask, or, better, one of the ‘beakers,’ or thin tumbler-shaped vessels, so largely used in chemical laboratories; partially fill it with ordinary household water, and then place it over the flame of a spirit-lamp, or Bunsen’s, or other smokeless gas-burner. Carefully watch the result, and the following will be observed: first of all, little bubbles will be formed, adhering to the sides of the glass, but ultimately rising to the surface, and there becoming dissipated by diffusion in the air. This is not boiling, as may be proved by trying the temperature with the finger. What, then, is it?