The custom of placing an inverted cup in a fruit pie, the cook will inform us, is to contain the juice while the pie is baking in the oven, and prevent its boiling over; and she is the more convinced in her theory, because, when the pie is Withdrawn from the oven, the cup will be found full of juice. When the cup is first put in the dish it is full of cold air, and, when the pie is placed in the oven this air will expand by the heat and fill the cup, and drive out all the juice and a portion of the present air it contains, in which state it will remain until removed from the oven, when the air in the cup will condense, and occupy a very small space, leaving the remainder to be filled with juice;but this does not take place till the danger of the juice boiling over is passed. If a small glass tumbler is inverted in the pie, its contents can be examined into while it is in the oven, and it will be found what has been advanced is correct.