December 15, 1911] 



SCIENCE 



847 



balloon ascension from North Adams, Mass., 

 July 29, 1908, and three memoirs. The first 

 of these memoirs is by H. H. Clayton, on " A 

 Study of Clouds with Data from Kites." Mr. 

 Clayton has devoted himself so closely, for 

 years, to the study of clouds and of kite data 

 that this subject may in a very real sense be 

 called peculiarly his own. The investigation 

 is a very interesting one to all who have made 

 any observations of clouds, and throws much 

 light on many hitherto obscure points in 

 cloud formation. In fact, it is one of the 

 most suggestive discussions of the methods of 

 cloud formation which has been published. 

 The data used included all the measurements 

 obtained up to January, 1909. A series of 

 simple diagrams makes clear each step in the 

 discussion. Cumulus clouds are found to be 

 obviously caused by condensation in bodies of 

 ascending air. Alto-stratus, alto-cumulus 

 and cirro-stratus are probably formed in a 

 stratum of air which is rising at a slight angle 

 to the earth's surface. Strato-cumulus, on the 

 other hand, is formed by a combination of 

 local ascending currents and an ascending 

 sheet of cloud. All clouds are found to be 

 closely connected with inverted temperature 

 gradients, the top of the cloud being usually 

 in the coldest air immediately beneath the in- 

 verted gradient of temperature, and the 

 height at which cloud formation can take 

 place in the lower air being determined by the 

 height above sea-level of the lowest inverted 

 temperature gradient. The height above sea- 

 level of the lowest inverted gradient of tem- 

 perature and the complement of the dew-point 

 determine whether days shall be cloudless or 

 partly cloudy. There is thus a possibility of 

 making practical use of the temperature and 

 humidity observations obtained in the free 

 air by means of kites and balloons for pre- 

 dicting the probable formation of various 

 clouds, and therefore the probable weather 

 that will follow. Mr. Clayton has left the staff 

 of the Blue Hill Observatory, with which he 

 was connected for nearly 23 years. His work 

 there is well known to meteorologists the 

 world over. His present study of clouds is 

 perhaps the last memoir by him which will ap- 



pear in the Annals of the Harvard College 

 Ohservatory. It seems to us singularly ap- 

 propriate that this particular study should 

 have to do with kites and clouds, two lines of 

 investigation which Mr. Clayton has done so 

 much to further, and in which he has so un- 

 usually distinguished himself. 



There are two further discussions, by An- 

 drew H. Palmer, who has recently joined the 

 staff of the observatory as research assistant, 

 after leaving the graduate school of Harvard 

 University. The first of these, on " Wind 

 Velocity and Direction in the Free Air," 

 deals with a subject concerning which the 

 Blue Hill observations are able to supply val- 

 uable original data. There were used in this 

 study the data obtained during 234 kite 

 flights, made in 1897-1908; the cloud observa- 

 tions of 1890-91 and of 1896-97, and the 

 hallons-sondes data from St. Louis, 1904r-07. 

 The principal results are as follows: (1) the 

 general increase in velocity with height; (2) 

 the rare occurrence of gusts of wind above 

 low heights; (3) the frequent clockwise and 

 occasional counter-clockwise changes of direc- 

 tion with height; (4) the shallow character of 

 easterly winds; (5) the relative frequency of 

 ascending currents as compared with those 

 descending. It is easily seen that such results 

 as these are of immediate practical importance 

 in connection with aviation. Indeed, it is 

 significant that both Mr. Clayton's stud.y of 

 clouds above referred to, and this one of Mr. 

 Palmer's have such distinctly practical bear- 

 ings. 



A second paper by Mr. Palmer concerns 

 "Pressure Oscillations of Short Wave- 

 length." It appears that the pressure oscilla- 

 tions of short wave-length at Blue Hill are of 

 two types, (1) those of 1-3 mm. amplitude, re- 

 curring irregularly over a period of several 

 hours, and (2) those consisting of a single 

 wave of 2-3 mm. amplitude occurring with 

 certain thunderstorms. The former are due 

 to the undulations set up at the horizontal 

 boundary between two air strata of which the 

 upper is the lighter, and in which the rate or 

 direction of movement of one differs from 

 that of the other. Type (2) seems to be 



