The third important consideration in planning a good tropical house is that the outer walls should, as far as possible, be shielded from the direct rays of the sun by ample verandahs. Objects exposed to the full glare of the sun soon become so hot that it is difficult to handle them, reaching a temperature 40° or 50° F. higher than that of the air, and though building materials conduct heat but slowly, they do so very surely, so that the air within any building with extensive unshielded sunward walls cannot fail to be considerably hotter than that of one so planned that as small an area of wall as possible is directly exposed. Within the true Tropics, the sun must necessarily come to the northward of any localities for a longer or shorter portion of the year, and in such low latitudes it is desirable that the verandah should extend all round the house; but outside the equatorial zone the side looking away from the noon-day sun may be left unprotected as far as the coolness of the house is concerned; though a northern verandah is still desirable, as affording the most eligible position for an open air lounge during the day. Within practicable limits, a verandah can hardly be too wide, and as one of its main functions is to shield the main wall, it is also important that it should be high pitched, but this point is too often lost sight of, although the additional cost of constructing a higher-pitched verandah is very small, as the supports of these structures cost but little, in comparison with the roof. Of course the oblique rays of the sun will search into a high verandah for a longer time than they can in a low one, but this defect is easily obviated by closing the upper part of the colonade with wooden jalousies or with mats, but in this case openings should be provided in the roof to give exit to what must be almost dead air. Verandahs of less than six feet width are of comparatively little use, and 10 feet may be considered to be a fair average standard, but 15 feet is by no means excessive, if it can be afforded, and as shown in the diagram on page 9, double verandahs, consisting of two colonnades, each about 12 feet wide, are by no means uncommon in Persia.