16 MISSOURI BOTANICAL GARDEN. 
ference it shows between the average precipitation of the 
last thirty-one years and the comparable average obtained 
by Dr. Engelmann * for a period of twenty-three years 
ending with 1861, and I have added to the diagram the 
dotted line, 3, representing his averages, amounting to 
44.92 inches for the year. 
The monthly distribution of rainfall for 1901, 1, as 
compared with the average for the preceding thirty-one 
DIAGRAM C. 
50 or] 
43 
ee. 
so —-40 INF 
ee at eee 
DP, eee oe gal 
ame i 30 IN- 
Pa Lone 
Be oe Se ee 1 
4 ae} 
ie gn 
etaget ————t-20 IN 
a et $d 
Pe So ae 
- ae — ame 10 IN- 
ae "| 
a eal 
PAN. FEB. MAR. APR, MAY JUNE JULY AUG. SEPT... DCT. NOV, DEC 
PRECIPITATION — CUMULATIVE. 
years, 2, and the average for the twenty-three years cov- 
ered by Dr. Engelmann’s observations, 3, is more clearly 
shown on the diagram marked D, compiled from the same 
sources as the preceding one. If reliable, the curves on 
these two diagrams show that though slightly heavier 
toward the end of winter than formerly, the rainfall has 
very much decreased in the last forty years, and, unless the 
variations from year to year are too great to permit of the 
drawing of even approximately trustworthy averages from 
such periods of time as twenty or thirty years, they appear 
to indicate a change in climate which is not only hard to 
explain but which, if it continues, may within a compara- 
* Trans. Acad. Sci. of St. Louis. 2375-9. 
