At the close of this volume, drawings, prepared by Mr. Lewis Leeds, are given, more fully to illustrate this mode of warming and ventilation, and in so plain and simple a form that any intelligent woman who has read this work can see that the plan is properly executed, even with workmen so entirely ignorant on this important subject as are most house-builders, especially in the newer territories. In the same article, directions are given as to the best modes of ventilating houses that are already built without any arrangements for ventilation. V. THE CONSTRUCTION AND CARE OF STOVES, FURNACES, AND CHIMNEYS. If all American housekeepers could be taught how to select and manage the most economical and convenient apparatus for cooking and for warming a house, many millions now wasted by ignorance and neglect would be saved. Every woman should be taught the scientific principles in regard to heat, and then their application to practical purposes, for her own benefit, and also to enable her to train her children and servants in this important duty of home life on which health and comfort so much depend. The laws that regulate the generation, diffusion, and preservation of heat as yet are a sealed mystery to thousands of young women who imagine they are completing a suitable education in courses of instruction from which most that is practical in future domestic life is wholly excluded. We therefore give a brief outline of some of the leading scientific principles which every housekeeper should understand and employ, in order to perform successfully one of her most important duties. Concerning the essential nature of heat, and its intimate relations with the other great natural forces, light, electricity, etc., we shall not attempt to treat, but shall, for practical purposes, assume it to be a separate and independent force. Heat or caloric, then, has certain powers or principles. Let us consider them: First, we find _Conduction_, by which heat passes from one particle to another next to it; as when one end of a poker is warmed by placing the other end in the fire. The bodies which allow this power free course are called conductors, and those which do not are named non-conductors, Metals are good conductors; feathers, wool, and furs are poor conductors; and water, air, and gases are non-conductors.