NO. 10 SOLAR RADIATION AND WEATHER STUDIES ABBOT 1 3 



be combined to determine their mean forms. Interferences from other 

 periodicities and from accidental errors are largely eliminated when 

 occurring in different phases in so many independent cases. 



As stated above, an 8-month periodicity in solar variation was seen 

 by the first inspection, and this was first determined. Then the original 

 curve was modified by subtracting from its ordinates a sufficient num- 



Table 3. — The ii-month Periodicity in Solar Variatioti" 



General 

 Jan. i920-July 1924 Mean Aug. 1924-Jan. 1930 Mean Feb. 1930-Aug. 1934 Mean Mean '' 



68 59 58 28 43 SI 47 52 37 44 45 3° 43 36 44 54 33 42 42 1.9421 



67 57 SI 24 40 48 38 54 43 41 42 30 41 43 43 SO 28 44 42 1.9431 



60 48 S3 16 40 43 29 48 41 44 44 31 40 46 42 44 29 43 41 1.9437 



60 62 so 29 41 48 39 51 42 so 43 30 43 43 40 59 37 41 44 i-944i 



57 53 48 26 41 4S 49 44 44 45 49 38 45 39 44 53 4i 48 45 1-9445 



58 48 47 22 39 43 4S 44 41 46 45 35 43 39 41 55 4i 39 43 1-9446 



• 9447 



60 41 38 27 34 40 so 57 41 48 44 36 46 42 32 55 46 49 45 



49 53 45 22 42 42 SI 46 39 45 49 33 44 40 45 65 41 46 47 1-9447 

 34 54 49 29 39 4i 50 49 40 47 45 34 44 41 47 55 34 48 45 1-0443 



50 S4 46 32 39 44 47 40 39 45 44 35 42 42 46 47 SO 55 48 I.944I 

 56 38 52 21 38 41 49 47 37 43 39 33 4i 41 45 56 45 Si 48 1-9435 



51 40 50 16 21 36 45 46 42 44 40 33 43 41 37 S3 46 SI 46 1-9431 

 48 46 46 24 36 40 44 4S 36 42 39 33 40 43 36 60 47 62 so 1.9424 

 S8 43 42 33 40 43 50 48 38 41 32 32 40 43 49 62 40 46 48 1.9418 



48 45 34 15 42 31 41 44 32 47 36 35 39 40 48 s6 37 46 45 1-9407 

 42 50 32 25 38 37 46 42 32 43 39 33 39 44 45 52 37 47 45 1-9404 

 33 49 30 29 38 36 39 43 30 41 34 35 34 SO 51 47 46 45 48 1.9396 



38 51 24 28 39 36 46 44 33 41 22 32 36 45 49 41 32 SI 44 1-9389 

 45 29 21 30 4S 34 39 37 37 44 29 29 36 42 57 33 37 60 46 1.9384 



39 42 29 23 42 35 47 39 37 43 33 28 38 41 51 35 35 45 4i 1-9376 



49 38 22 30 41 36 40 J3 37 43 28 31 35 39 43 42 39 40 41 1.9371 

 27 53 19 27 41 33 42 3S 41 42 25 29 36 39 49 43 39 42 42 1.9365 

 25 54 14 30 43 33 36 42 39 36 29 31 36 35 51 32 39 41 40 1.9362 

 31 SO 12 35 43 34 41 31 36 36 31 30 34 42 45 36 35 37 37 1-9359 

 51 46 00 20 41 32 43 38 37 35 31 31 36 39 46 31 36 46 40 1.9361 



44 57 12 35 43 36 48 39 42 31 29 35 37 40 47 29 39 44 40 1.9366 



45 36 21 34 45 36 44 35 42 36 34 40 39 4i 44 26 35 38 37 1.9374 



44 58 14 35 SO 40 44 32 37 44 30 39 34 4i 49 30 28 48 39 1.9385 

 54 54 17 29 52 41 49 38 43 4i 33 37 39 4i 44 36 34 42 39 1-9392 



40 48 20 46 53 41 53 42 43 42 31 37 41 35 51 30 38 41 39 1.9398 

 53 54 21 44 46 44 43 39 42 47 31 35 40 41 47 23 38 44 39 1.9401 

 49 60 15 40 49 43 44 38 43 46 25 39 40 45 46 18 40 43 38 1.9406 



45 53 20 40 41 40 49 42 43 46 30 37 40 41 40 32 42 45 40 1. 9410 



" The figures in the table are to be understood as subjoined to 1.900. Thus, for 68 read 

 1.968 calories, etc. 

 * Computed from smooth curves representing the three groups. 



ber of successive repetitions of the mean form of the 8-month peri- 

 odicity. Thereupon inspection seemed to indicate an ii -month peri- 

 odicity. With this also removed, a /-month periodicity showed itself. 

 Proceeding in this way, periodicities of 7, 8, ii, 21, 25, and 45 months 

 were successively removed." The residual curve remaining after their 

 removal showed very plainly as its major feature a periodicity of 68 

 months. It has the largest amplitude of any of the solar periodicities. 



*In our latest analysis, extending from 1920 to 1934, additional solar periodici- 

 ties of 9I, 34, 39i, 92 months, and one of 23 years were added to the above list. 



