44 THE ADIRONDACK SPRUCE 
arately for those whose growth was accelerated. These 
trees occurred on eleven of the sample plots which were 
studied at Santa Clara. The other three plots were 
omitted because only a very few trees were taken at 
the first cut, and almost none of the remaining small 
trees showed accelerated growth. These measure- 
ments exhibit the rate of growth under various condi- 
tions of situation and soil. 
The figures of diameter growth given in the following table were 
derived from measurements of the last ten rings. For example, 
the third column gives the average rate of growth of all trees just 
before the last cutting, and was found in each case by subtracting 
the increment for the period since lumbering from the increment 
for the last ten years, and dividing by the nnmber of years during 
which the growth thus ascertained was made. The fifth column 
gives the average rate of growth of all trees since the lumbering, 
whether they show an increased growth or not. The column 
which gives the current annual growth in diameter after the values 
have been made regular by a curve also requires a word of explana- 
tion. When a series of averages are made out it often happens 
that the successive figures do not follow quite regularly. It will 
be noticed in the table that this is true of the lower part of the 
fourth column, and that it is probably explained by the lack of 
enough trees of 15 inches in diameter to get a fair average. In 
such cases the values are plotted on cross-section paper and a 
regular curve is drawn through or near the points which represent 
them. The points through which the curve actually passes are 
then taken as the true values. In this way accidental irregularities 
are avoided, and the results are brought much nearer the truth. 
