The graphical presentation of experimental data in the physical sciences has several advantages which today are too familiar to require very detailed enumeration. Its greatest strength lies in the clarity and succinctness with which it displays the information contained in tabulated results: for the experimenter a graph provides a rough and immediate check on the accuracy and suitability of the methods he is using, and for the reader of a scientific report it may convey in a few seconds information that (...) could only be gleaned from a table of measurements by hours of close study. There are occasions whereonlythe analysis of experimental graphs will provide the information we require, but usually the actual analysis of results is carried out nowadays by computational methods. The use of graphs is therefore not so much a necessary part of scientific procedure as an extremely useful one, and one that is often taken very much for granted. (shrink)