exact position. Not only are the curves themselves shown on the screen, but the whole face of the card is seen so that the figures for any points on the curve which are of special interest may be read directly from the screen.
If the information or record room is large enough to serve for holding conferences the lantern and the screen may be installed permanently as part of its equipment. Ordinarily, however, it will be found best to have the record room more private than any room used for general conferences can be made, and the lantern would be part of the equipment of the conference room rather than of the record room. 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 equipped 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. The cards for those houses which made particularly good records could be shown, the records could be commended, and conclusions could be drawn as to how the success had been attained. Records for the less successful houses could also
