792 JOURNAI, OF FORESTRY 



the annual rainfall was correlated with a drop in wood formation, 

 while in other years a decrease in precipitation was not accompanied 

 by a corresponding decrease in wood growth. In some cases a low 

 annual precipitation appeared to show its effect in decreasing the 

 growth in the following year. 



As annual precipitation measured from January to January does not 

 correspond with the period of physiological activity in the tree's growth, 

 the author attempted to correlate precipitation for groups of months 

 with diameter growth and with somewhat better success, but even here 

 unexplained irregularities are not infrequent. On page 8 it is stated 

 that a low annual precipitation apparently shows its effect in the fol- 

 lowing year. Thus the small rainfall in 1910 and decreased ring 

 growth in 1911. On the next page, however, data is presented to show 

 that the precipitation of one year does not show its effect the following 

 year. Thus the heavy precipitation in 1893 had no apparent effect in 

 influencing the small diameter growth of the next year due to the low 

 rainfall of that year. 



The best correlation of rainfall with ring width was found in the 

 comparison of the total rainfall in March, April, May, and June with 

 annual ring width. According to the author ring width varies directly 

 with the precipitation for the above months and inversely with the 

 temperature for May and June. A table is presented showing this 

 correlation. The sum of calculated ring width values over a period of 

 thirty years, based on rainfall and temperature, was fotmd to be 3.1:59 

 inches as compared with the observed values of 4.574 inches. The 

 author by inspection introduces a factor which brings the calculated 

 values more closely in agreement with the observed values. This fac- 

 tor he assumes to be an approximate expression of the normal growth 

 tendency of the oaks under consideration. His conclusion is that the 

 average ring width for. the past thirty years in the oaks studied was 

 largely determined by three variables, namely, the gradually changing 

 factor which may be age, the rainfall for March, April, May, and 

 June, and the temperature for May and June. He also concludes that 

 variations in ring width from year to year were largely determined by 

 variations in two factors, namely, the rainfall for the four months 

 mentioned and the temperature, for the two months mentioned above. 



This investigation, although developing an ingenious method for 

 correlating ring width with temperature and precipitation, cannot be 

 accepted as final in its results and adds little to our present knowledge 



