4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, IO7 



12 months, these being averages taken over 22 years from 1924 to 

 1945. The results are shown graphically in figure 2. There is a slight 

 departure from exact intervals of 6.6456 days between maxima, but 

 the intervals between minima are as close to the correct interval as 



Table 2. — Precipitation at Washington in the solar period 6.6456 days. Phases adjusted. 

 Mean values in inches per day, the 12 months, 1^24-194$. Prefix 0.0 or 0. 



Days — s — 4 — 3 — 2 — I o i 2 3 4 s 6 7 8 9 10 11 12 13 14 



Jan 812 873 loss 1628 1476 60s 9S3 797 709 1246 1367 1031 73s 821 S2S 877 1744 1546 484 1093 



Feb 947 801 509 IIS2 1245 895 1044 842 587 820 1133 1019 1115 792 980 777 898 1563 iS34 "76 



Mar 1034 995 728 1312 1346 1012 870 iios iis8 1018 1178 looi 1205 1177 851 1336 1143 1068 1226 



Apr 939 1294 929 1972 1236 I0S9 920 903 1321 1036 1000 1663 1216 1052 638 862 972 1149 1378 784 



M!ay 777 999 1182 687 1188 1484 I07S 623 1073 1164 830 iS7i "99 7" 966 1127 695 1025 128s 



June 899 670 IS4I 941 1181 2128 822 1009 1048 1392 ISSS 1196 1570 787 944 i6s4 1624 1135 1610 



uly 1061 691 123s 1246 173s 1183 1122 634 856 mo 1427 1977 980 748 48s 1347 1378 1224 1314 



Aug 2136 1256 issS 1509 1390 1857 1826 1615 1094 1899 1234 2489 1665 1610 928 1464 1944 1779 1090 1662 



Sept 2007 1147 1035 1324 1619 1090 1316 i6s4 1159 923 1354 2167 379 1272 1262 66s "18 1397 1586 



Oct SSS I2I0 S5S 1301 1475 132S 620 671 869 1045 901 1079 1103 860 991 513 1322 834 1069 1068 



Nov S07 I0S4 675 821 iggi 730 380 773 696 1026 1631 1230 634 646 845 938 940 1040 1470 



Dec 901 558 797 752 1089 680 927 774 1014 846 1104 907 647 802 1019 1168 1033 657 514 



Means 1126 949 1017 1163 1286 1338 loio 910 947 1125 1141 1593 1092 928 862 1000 1261 1230 1177 1114 



/600 



Fig. 2. — Graph of average effect, 1924 to 194S, all months, of the 6.6456-day 

 solar period on Washington precipitation. Abscissae, days. Ordinates, inches/ 



10,000, 



can be shown without taking account of hours. The range of the 

 effect is from 0.0862 to o. 1 593 inch, a range of 85 percent. 



It is indeed a pity that the shiftings of phase occurring with precipi- 

 tation, as with temperature, are of unknown causation. If their causes 

 could be found and the phase changes could be anticipated, here would 

 be a valuable aid for forecasting. Perhaps it may have a valuable 

 significance that the phase changes for precipitation are identical with 

 those for temperature. 



