There is an advantage in having one man put all the cards back in the files, as in this way there is less chance of the cards being misplaced in the file than if several different executive officers were to use the cards and themselves put the cards back. It should be stated here that in the ordinary use of curve files such as are shown in Fig. 217 an executive would not need to remove the cards from the drawer. He would simply turn the cards over one at a time, raising any card of special interest about three inches to look at it, but not removing it sufficiently to cause any danger of restoring the card in a wrong position. It is only when cards for a series of years are taken out and laid down for comparison with some other series of cards that there is any necessity for removing the cards from the drawer.

The Westinghouse Electric and Manufacturing Company of Pittsburgh regularly plot about four thousand curves which record the

296 GRAPHIC METHODS

activities of all departments of the business. The majority of the curves have one more point added each month, but some of the curves are on a weekly basis. Day and Zimmermann, of Philadelphia, are plotting a total of about eight thousand curves, most of the curves on a cumulative basis somewhat as shown in Fig. 134. In order to allow space enough for a cumulative curve (which naturally takes up more room than a curve plotted on a non-cumulative basis), the curves are plotted on cards 8}^ inches by 11 inches, and these cards are filed vertically in a tray desk so that a man sitting at the desk can instantly lay his hand on the proper card for any one of the eight thousand curves.