1011. Baking Powders and Egg Powders.--These useful preparations are now much used in making bread and pastry of all kinds, and have the merit of being both cheap and wholesome. They may be procured of all grocers and oilmen. The basis of all baking powders consists of carbonate of soda and tartaric acid or cream of tartar, and egg powders are made of the same materials, with a little harmless colouring matter such as turmeric. By the action of these substances, carbonic acid is generated in the dough, which causes it to rise in the same manner as the so-called "aërated bread" made on Dr. Daughlish's system, by which carbonic acid is forced into the dough before baking.