The use of more lines than necessary should be avoided as it tends to cause confusion. See Fig. 119 as another method of charting the same data

In order to determine just how closely the price of apples depends upon the supply, Fig. 119 was prepared from the data of Fig. 118. Though the dots in Fig. 119 represent a rather long series of years, they nevertheless have a fairly symmetrical arrangement and the general tendency might be approximated by a smooth curve drawn as shown. It must be remembered that there are many conditions which may affect the position of these dots on the chart. For one thing.

COMPARISON OF CURVES

Price per Bbl $eoo

the standard of living has very greatly changed in the period of time from 1895 to 1912. Prices in recent years might be expected to be considerably higher than in the earlier years, without any regard to the size of the apple crop. Besides this, numerous diseases have affected apple trees in recent years, requiring more care than formerly to produce good fruit. This would also have some tendency to raise prices in spite of the tremendous number of apple trees which have

come into bearing in the later portion of the period of time under consideration. The general method of plotting shown in Fig. 119 is of great importance and it should be kept in mind whenever two curves are found having similarities such as are seen in Fig. 118. Other examples of this method of plotting to study the correlation of two related