KIMBALL AND MILLER: CLOUDS AND RADIATION 377 



The course of events at each locality, affecting the height of 

 the barometer, appears to be substantially as follows: (1) A 

 forced forenoon compression ,of the atmosphere followed by its 

 equally forced afternoon expansion ; the two together forming one 

 complete barometric wave, with a 10 o'clock maximum and a 

 4 o'clock minimum, in harmony with the free vibration of the 

 entire atmospheric shell. (2) Non-disturbance thru the night, 

 or during the period of a single free vibration. (3) Repetition 

 the following day of the forced disturbances in synchronism with, 

 and therefore at such time as to reinforce, the free vibrations. 



The series of disturbances of course is indefinitely great, alter- 

 nately forced and alternately free, but the resulting amplitudes 

 of the barometric changes are limited, thru friction and thru the 

 absence of perfect synchronism, to comparatively small values. 



METEOROLOGY. — Note on the influence of clouds on the dis- 

 tribution of sotar radiation. H. H. Kimball and E. R. 

 Miller. To appear in full in the Bulletin of the Mount 

 Weather Observatory. 



The Callendar pyrheliometer as ordinarily exposed gives a 

 continuous record, on a drum revolved by clockwork, of the inten- 

 sity of the vertical component of the radiation received from both 

 sun and sky. It is a matter of common observation, subcon- 

 scious in most cases, that with favorable relative position of 

 clouds and sun the solar rays are concentrated. Records obtained 

 by means of the Callendar pyrheliometer at Mount Weather, Va., 

 and Madison, Wis., afford several interesting examples of in- 

 creased radiation intensity due to such concentration of the 

 sun's rays. A few of these records are reproduced in the more 

 extended note that will appear in the Bulletin of the Mount 

 Weather Observatory. They set forth more clearly than can 

 words the results here given. 



At Madison, on February 5, 1912, at 10.40 a.m., a glaringly 

 bright sheet of alto-stratus cloud advanced from the northwest. 

 The recording pen of the register rose as the cloud approached 

 the sun; attained a maximum of 1.11 gram-calories per square 

 centimeter per minute when the edge of the cloud reached the 



