With this arrangement it will be necessary to take the curve cards from the record room to the place where the lantern is installed. The file for the curve cards (see Fig. 217) had better be ecjuipped with spring locks so that there will be no danger, when the file is carried, of drawers slipping out and spilling the cards. A rod arrangement is never desirable with such cards as these, for the rod would spoil the bottom portion of the card and would also make it impossible to lift cards out for quick reference or comparison. Brass handles on the sides of the file case would make it easy to carry the case to the conference room. There, on a table beside the lantern, the cards in the file case would be available for use almost exactly as lantern slides are used with the ordinary lantern. In fact, the arrangement of the cards is even more convenient than the usual arrangement of lantern slides in that the cards have a guide index so that any desired card may be instantly located.

An executive who wishes to have a meeting of his department heads need not make any very definite plan before the meeting begins as to what cards he is to show on the screen. He can start talking to his men, and, at pleasure, ask the lantern operator (ordinarily the statistician) for any set of curve cards which may be of interest to him at the moment, or which may be referred to at any time during the discussion. The use of curves on a lantern screen in the manner suggested would entirely revolutionize the meetings of the department heads of a business, or the meetings of branch-house sales managers. In sales work especially, the use of the various cards would make it possible to show the whole assembly the recent records made by selling houses in the different parts of the country.