Mat 12, 1911] 



SCIENCE 



739 



principles have been recognized. For ex- 

 ample, if one knows the barometric gradient 

 at the ground he can compute approximately 

 the velocity of the wind for moderate heights 

 with the aid of Ferrel's formula and the 

 known rate of increase of velocity with height. 

 Moreover, the change of wind direction with 

 height can be foretold when one's position 

 with respect to the barometric distribution is 

 known. Such information is of value both to 

 the aeronaut, who in the free balloon seeks a 

 desirable current by ascending or by descend- 

 ing, and to the aviator, who in an aeroplane 

 can travel more advantageously with the wind 

 than against it. In the opinion of Mr. Dines, 

 progress in the art of mechanical flight de- 

 pends largely upon meeting and overcoming 

 the difficulty of the gustiness of the wind. 

 Many accidents have had their origin in this 

 condition, which is always present in a more 

 or less degree. When it is serious enough to 

 render flying hazardous the professional avi- 

 ator aptly says that the air is " full of holes." 

 In various ways it has been determined that 

 the wind becomes steadier with increasing 

 height, except within the stratum of fracto- 

 cumulus clouds, when they are present. In- 

 creased speed does not result in increased sta- 

 bility unless the construction of the aeroplane 

 is proportionately strengthened. These, and 

 other facts based upon the meteorological data 

 of Blue Hill Observatory are shown graphic- 

 ally, as well as verbally, in a book called 

 " Charts of the Atmosphere for Aeronauts and 

 Aviators," which is now in the hands of the 

 publisher, John Wiley and Son, of New York. 



A TEMPERATURE model, the second of its 

 kind,' has recently been completed by Mr. 

 Eugene Van Cleef, of Chicago. Based upon 

 the data for the period 1890 to 1910, inclusive, 

 it shows in relief the average hourly tempera- 

 tures for that city. Of plaster-of-paris con- 

 struction, it is two feet long and one foot 

 wide. Vertical lines at inch intervals are 

 drawn upon the two narrow sides to represent 

 the months of the year, while similar lines 

 drawn upon the other two sides represent the 

 twenty-four hours of the day. The vertical 



' See Science, Vol. XXXI., No. 807, p. 954. 



dimension of each point upon the upper sur- 

 face of the model represents temperature, each 

 sixteenth of an inch representing one degree, 

 the base being zero degrees Fahrenheit. The 

 upper surface is anticlinal, and is colored to 

 show the four seasons of the year. The model 

 is instructive in many ways, the more striking 

 features shown consisting of (1) the diurnal 

 periodicity of temperature, (2) the change in 

 the occurrence of the daily minimum tempera- 

 ture from about 6 a.m. during winter to 

 4:30 A.M. in summer, (3) the change in the 

 occurrence of the maximum temperature of 

 the day from about 3 p.m. in winter to about 

 1 P.M. in summer, and (4) the more rapid 

 increase of temperature from spring to sum- 

 mer than the decrease from autumn to winter. 

 In the neglected field of phenological cli- 

 matology a noteworthy contribution has been 

 made by Dr. E. Vanderlinden in his " Etude 

 sur les phenomenes Periodiques de la Vegeta- 

 tion dans leurs Rapports avec la Variations 

 climatiques." The latter describes the results 

 of a study of the relation between climate and 

 the flowering-date of thirty-nine plants, as 

 observed at the Royal Observatory gardens in 

 the suburbs of Brussels, during the fourteen 

 years, 1896 to 1909, inclusive. Though the 

 observer was the same throughout the period, 

 all of the plants were not observed each year. 

 The first appearance of the stamens was taken 

 as a basis, since leaves and seeds develop ir- 

 regularly. When possible, artificial condi- 

 tions were produced to verify conclusions 

 based upon the observations of the effects of 

 similar natural conditions. The effect upon 

 the flowering date of a plant by departures 

 from the mean of the various meteorological 

 elements affecting its growth was the real ob- 

 ject of the study. Rainfall and atmospheric 

 humidity had less effect in this respect than 

 is generally supposed to be the case. Radia- 

 tion, too, especially during the spring months, 

 is comparatively unimportant. By far the 

 most effective factor in determining the time 

 of florescence is the temperature, though its 

 importance varies with the different stages of 

 the plant's life. Varieties accustomed to 

 mature at about the same time are affected 



