8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 



long periods from over-riders, applicable both in radiation and in 

 precipitation. 



3. LONG-RANGE PREDICTION OF PRECIPITATION 



It is urged by experts in meteorology that exact measurements of 

 precipitation are so difficult, its local distribution so extraordinarily 



Table 2. — Harmonic Periods in Rochester, N.Y., Precipitation 

 Exact Fractions of 273 Months, Category 2 Only 



irregular, its jumps between zero and super-normal amplitude so 

 erratic that 50 years of observation are hardly enough to give satis- 

 factory monthly normals. Hence they prefer to do research with 

 temperature and pressure, hoping through atmospheric circulation to 

 find a path to advance in the forecasting of precipitation. My former 

 chief, the late Dr. S. P. Langley, encouraged me to hope that knowl- 

 edge of solar radiation and of its atmospheric transmission might 



