228 THE MANUSCRIPT 



Presentation of results 



Tables and figures (graphs or other drawings) are the common forms 

 for presenting data. 



Figures: The preparation of illustrations requires a little knowledge 

 about the printing processes. The original photograph or drawing must 

 be reproduced by means of an engraving. The drawings furnished to the 

 engraver usually are done on white paper with black India ink. Because 

 reduction occurs in processing, the thickness of lines, the sizes of points 

 on graphs, and the proportions of the lettering must be chosen to show 

 clearly on the smaller picture. Some editors prefer good glossy photo- 

 graphs of the original drawings. Graphs may be drawn on coordinate 

 paper (graph paper) if the lines on the paper are blue, which does not 

 photograph. 



Most of the figures in this book were drawn in India ink on 8Vi by 1 1 

 inch sheets of tracing paper. Lettering was done with a Leroy lettering 

 set, a device in which the pen follows a prepared template. Several sizes 

 of templates and pens are available, and the right combination must be 

 chosen for the anticipated reduction in size of the printed drawing. 



Graphs are often a problem for the beginner. We might measure the 

 effect of temperature on the rate of a reaction, and the results would be 

 especially amenable to graphic presentation. We control the temperature 

 and measure the rates, so temperature should be placed on the horizontal 

 axis and rate on the vertical axis. Some other sets of variables are not 

 quite so obviously "independent" or "dependent." Mathematical exami- 

 nation shows that one is a function of the other, however, or y = f(:x:). 

 The length of a growing animal varies with time, not vice versa. The 

 absorption of light by a solution depends on concentration, not the other 

 way around. Either you control and vary the factor and measure its effect 

 or you observe the effect of some uncontrollable factor like time. In either 

 case the effect goes on the vertical axis. 



The scale of distances on the graph corresponds to numerical intervals. 

 If 1 cm stands for 1 min, then 10 cm stands for 10 min, even if measure- 

 ments were made at 1 min, 2 min, 3 min, 5 min, 10 min, 20 min, or 

 other odd intervals. Figure 17-1 shows a properly prepared graph, as well 

 as some graphs containing common errors. Imagine how these errors 

 would affect the conclusions that might be drawn. 



A table is the most efficient way of presenting numbers. The table 



