)930 1931 1932 1933 1934 1935 1936 1937

25.000 24.000 23.000 22.000 21.000 20.000 19.000 )6.000 17.000 16.000 15.000 14.000 13.000

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DAYLIGHT

How Charts Ought Not to Be Made

The omission of the zero line in this chart gives a false impression of the relative values of the number of accidents during the hours of darkness and

during daylight.

far been made measuring results from organized material carefully prepared and presented graphically.

The question is sometimes raised as to how you can present in graphic chart form, abstruse ideas which have not yet been reduced to words. Engineers and other people who are accustomed to using graphic methods are likely to approach the problem thinking graphically. They are apt to list the factors involved and then try different types of organization charts, etc., to work out the relations and size of the different factors.

■m}ft^?i(:i'f'WfS!i:iii,-m l*M !«• l«tO I9tl l»ll IttS IM4 Ittt l»t« t*tl Its* I9I* I«SO t«SI t«9t 1993 19S4 I99S t9SS I9S1

Ratio Chart Showing Prices of Non-Ferrous Metals in the United States fronts 1917 to 1937.

The above chart was reduced from one transmitted by Western Union automatic telegraph, showing that, as machines are installed, graphic charts may be sent from one city to another. Service is now available only in New York, Buffalo, and Chicago. Other cities will be added.

Graphic charts present unusually comprehensive data in condensed form for analysis and interpretation. Major libraries should contain a division of graphic charts. Filing most of the material could be easily done by placing material in the usual letter vertical files. Provision should, of course, be made for cross references. Probably it would be desirable to have two sections, one for scientific and technical data, the other to contain all other material.