60 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1935 



agreement. Of 66 forecasts, including 31 of temperature and 35 of 

 precipitation, 27 percent are of grade A, 42 percent of grade B, 17 

 percent of grade C, and 14 percent of grade D. 



Reverting to the levels of the Great Lakes, not only the 23-year 

 cycles, but apparently the double cycle of 46 years is of great impor- 

 tance. It appears to be associated with the drought which has oc- 

 curred in the northwest-central States since about 1930. It is, of 

 course, plain that the low lake levels are subject to a lag of perhaps 

 3 years behind the drought conditions which cause them. Hence 

 recovery may be expected several years before the return of the lakes 

 to normal levels. 



FIELD WORK 



Observations of the solar radiation have gone on regularly at Table 

 Mountain, Calif., Montezuma, Chile, and Mount St. Katherine, 

 Egypt. Besides the solar observatories, Mr. Butler, field director 

 at Montezuma, at his own initiative, has continued for several years 

 highly valuable seismographic observations there in cooperation 

 with the United States Coast and Geodetic Survey. Also, the as- 

 sistant at Montezuma, Mr. Maltby, has undertaken certain cosmic 

 ray work in cooperation with the Massachusetts Institute of 

 Technology. 



For several years the observers at Table Mountain, Calif., carried 

 on regular daily and nightly measurements of astronomical " seeing " 

 to assist in selecting the best location for the 200-inch telescope of 

 the California Institute of Teclinology. The " seeing " at Table 

 Mountain proved to be of the highest excellence. The observations 

 are now discontinued. 



The expedition of Messrs. Abbot and Aldrich to Mount Wilson, 

 referred to in last year's report, proved less successful than was at 

 first thought. The comparison of silver-disk pyrheliometers with 

 the standard water-flow instrument indeed was highly successful, 

 and a paper thereon has been published. But the investigation of 

 the extreme infrared solar spectrum, although incidentally leading 

 to a great improvement in the kampometer, a very sensitive radiation 

 instrument, requires further improvements of apparatus for success. 

 Observations were undertaken in cooperation with Dr. Joel Stebbins 

 on the energy spectra of the stars. In this experiment the stellar 

 spectral rays were selected by a battery of Christiansen filters, and 

 the intensities were measured by means of the Stebbins photoelectric 

 cell. Though apparently promising, the results were found to be 

 vitiated by stray light. This occurred because the photoelectric cell 

 is so disproportionately sensitive at certain wave lengths. It will 

 be necessary to substitute some other receiver, as for instance the 

 thermoelectric ceU, if energy spectra of the stars are to be observed. 



