Genetics: Goodspeed and Clausen

day, for air-mass ranges 1.3 to 4; 4 to 12; and 1.3 to 20 air-masses, respectively. All six solar constant values thus found fall between 1.90 and 1.95 calories. The smallest air masses, as it happens, yield slightly the highest values. We conclude that our previous results have not been made too small by neglecting to observe during the time when the sun is within 15° of the horizon. On July 11, 1914, in cooperation with the United States Weather Bureau, a recording pyrheliometer attached to sounding balloons was sent up to the altitude of about 24 km., where the barometric pressure was 3 cm. of mercury, which is only one twenty-fifth of that which prevails at sea level. Good records of solar radiation were obtained over a period of more than an hour, and including the period when the instrument reached highest elevation. The mean value of the best three records made at highest altitudes, as reduced to mean solar distance, comes out 1.84 calories per cm.2 per minute. We believe about 2% should be added to represent radiation scattered and absorbed in the atmosphere above the level reached, making for the probable value of the solar constant, from this day's work, 1.88 calories. This value falls decidedly within the range of solar constant values we have observed. We state in connection with it the following results which are the highest reliable direct observations of solar radiation at the various altitudes, as reduced to mean solar distance and vertical sun: