CHAPTER LIX.
SCIENCE AND DOMESTIC ECONOMY.
All branches of applied science are capable of giving us important hints and rendering us great service in all the conditions of our daily life, and as we have at various times throughout this volume mentioned useful domestic inventions applicable for use by means of water, air, etc., we may describe some more particularly relating to the inside of the house, and the science of domestic economy.
Fig. 885.—Double window.
Sometimes during the winter we may feel it very difficult, if not impossible, to keep the room warm. This we can do, however, by means of double windows.
Why is it that the double window as used in Russia keeps out the cold so well? Is it because the room is defended against frost by two windows instead of there being only one to resist it?—Not entirely. Such an explanation is not sufficient. If one be protected against the exterior cold, it is, thanks to the mass of air which is imprisoned, between the two windows. Extraordinary as it may appear, the air is a very bad conductor of heat, and forms the best insulator that one can find. The heat of the apartment is then perfectly retained by means of the air between the double windows.
In the same way the double window is not less useful during the summer, for it prevents the entrance of the heated air into the house. The double window may therefore be compared to the bournous of the Arab and the cloak of the Spaniard, which preserves from heat as well as guards against cold.
The double windows also perform another service. The glasses form a hot-house. The sun heats the air which is enclosed, and thus between the panes ferns and even vines will flourish. The windows are very easy to make, and in the event of any reader desiring to construct one or more, we give the dimensions. (See fig. 885.)
T T, is the exterior frame of the window. The two panes are mounted on a frame of wood, and are represented by A A´ and B B´ The sashes are represented apart, P and P´ are the shutters of sheet iron, which, if the walls be not so thick as represented, can be replaced by a spring-blind, which descends between the windows.
Sewing Machine worked by a Dog.