From what has been previously stated, it will be noticed that, as a rule, the architect in selecting the kind of material with which he will build his house is limited on account of expense to the first two types of construction—namely, the frame dwelling and the masonry house with wood interior. The latter two fire-resisting types are better fitted to the larger mansions, where expense is not so important an item. Undoubtedly the comparative costs between the various kinds of exterior walls will have much to do with the selection; but more often the local conditions will outweigh these considerations. In some places a house built of stone will be the best and most economical; in others, where there is an abundance of good sand, the cement house will be suitable, while those located near brick centres will find this material adaptable. The ideal method, of selecting a material of construction purely from an æsthetic point of view, is not always possible. But, after all, is not the most abundant local material the most harmonious to use for any one locality? Nature adapts her creations to the soil and the scenery into which she places them. All her animals are marked with colors which harmonize with the woods or fields in which they live. In fact this harmony is their protection, and in the war we imitated it in our camouflage painting. It is astonishingly evident, in the New York Museum of Natural History, how far more beautiful are animal tableaux which are set in painted scenery, representing accurately their natural habitat, than those which are exhibited alone in the cases, without a suggestion of their surroundings. Their marks and colorings seem ridiculous when they are separated from their natural surroundings. The same principle holds true in selecting the material for the small house. A stone house, built of native stone, in a stony, rugged region, is the most harmonious of all. A cement house in a flat, sandy country always seems in accord with the scene. A brick house in hills of clay most certainly appears the best, and a wooden house, near the great outskirts of the timber-land, is a part of the inspiring picture. Why are so many of the old colonial houses so charming? One of the reasons is the careful use of local materials. _Some Principles of Economical Design_ In the first architectural studies of the house, since this problem of cost is ever with us, it is well to be familiar with some of those broad and general principles of economical design.