ANALYSIS OF SOLAR RECORDS 75 



mated cycle lengths and he happily gets away from insistence on some special 

 curve of variation, such as a sine curve. His cycles are assumed to continue 

 unbroken through the data but one notes that his "eye" method of finding 

 cycles, just referred to, permits recognition of discontinuity in cycles and 

 hence aids in the selection of preferred data. By his skilful treatment he has 

 brought out the cycles expressed in the accompanying periodogram, figure 

 31b. On checking his results we found, as he did, a good cycle at 8.0 months, 

 a very strong one at 11.0 months (Schulman put it at 11.2) and possible 

 shorter cycles at 2.5 and 5.0 months and 3.4 and 7.0 months. Our method 

 did not lead us to give weight to our results in longer cycles. Plate 19B shows 

 cyclograms of his original curve (Feb. 1932) at 8 and 11 months. 



Abbot's synthetic curve B (see his paper of February 1932) combining 8, 

 11, 25 months and others longer, gives 8 and 11 months apparently not quite 

 as strong as in the originals. His residuals, C, have apparently no 11-months 

 cycle but still contain traces of 8-months cycle, distorted because the original 

 varied in amplitude. We found evidence of a lS^-month cycle and Schul- 

 man placed a faint cycle at 12.1 months. While no striking resemblance be- 

 tween Abbot's radiation curves and monthly sunspot numbers shows since 

 1919, using the data as they are, a resemblance may be seen between his radia- 

 tion cycles and the general periodogram of monthly numbers. 



The existence of a terrestrial cycle having the same length as the sunspot 

 cycle but showing two maxima, usually unequal, instead of one, has raised 

 the question : By what physical means could a single-crested cycle in the sun 

 produce a two-crested cycle on the earth? It has been suggested that such 

 a result might happen if a force acting from the sun upon the earth produced 

 an inverted effect when exceeding some critical value. Along this line Ab- 

 bot, for instance, has found a temporary, strong reduction in solar constant 

 in the presence of an extra large spot. Bollinger has worked out a formula 

 of relation of radiation to smoothed annual sunspot numbers that could pro- 

 duce a "Hellmann" effect or a double-crested resultant curve in radiation to 

 a single-crested original sunspot curve. Clements has observed an inversion 

 of relation between drouths and sunspot numbers when the latter rose in 

 value above 90. Clayton has found reversals of phase in climatic cycles. 



We found above that Abbot's radiation study shows cycles strikingly 

 similar to the general periodogram of cycles in monthly sunspot numbers, 

 but that during his observations, 1918 to 1931, the agreement is restricted in 

 two cycles, 7.9 months, a strong cycle, and 25 months, a weak cycle. Inver- 

 sion of reaction is intimated in some of Abbot's diagrams. 



PETTIT'S ULTRA-VIOLET RADIATION CURVES 



Pettit's ultra-violet radiation measures show something quite different 

 from Abbot's data. When we speak of heat radiation as measured by Ab- 

 bot, we include all wave lengths, knowing that most of the heat energy is in 

 the long waves, and that this energy comes rather generally from the sun's 



1 Abbot finds a 13.6 month cycle well marked in weather; see Bibliography, 1935. 

 See also his solar radiation analysis therein. See reference to 28-month cycle in I, 106. 



