SCIENCE 



[Vol. LVI, No. 1452 



somewhat greater detail than the former. 

 These publications bring together ithe best data 

 available approximately i-epresentative of lati- 

 tude 40° in central and eastern United States; 

 they carry the values to altitudes that are much 

 higher than aviation -n-ill ever need, and which 

 will only be exceeded -by the ordinates of the 

 most extraordinary trajectories in artillery 

 practice. 



Turning again to the Survey, we find that 

 the infoi-mation is conveyed largely by charts 

 and tables. The former present the matter as a 

 whole, showing the vertical and geographical 

 distribution of the several meiteorologieal ele- 

 ments over the entire central and eastern United 

 States. The latter are more precise, and are so 

 conveniently arranged thait the basic computa- 

 tional material for innumerable aerologieal 

 studies may be found there awaiting the stu- 

 dent. The text is brief, but clear and cogent, 

 and calls attention to the significant features 

 of the "survey." 



The summary is abased not only upon the 

 kite stations of the "Weather Bureau at present 

 operating (Due West, S. C, excepted, since 

 this sitation has been in operation only about a 

 year and a half) but also upon the records of 

 the Blue Hill Observatory and the Mount 

 Weather Observatory. Thus data from eight 

 aerologieal stations fairly well distributed, 

 whose records vary from .albout two to seven 

 years, have formed the hasis of the siirvey. 



The author shows that the values based upon 

 a five-year record do not vary to any significant 

 extent from those hased upon a three-year 

 record. As one might expect, the differences 

 between the averages of the three and five-year 

 record 



... are greatest at or near the surface, where 

 they amount in a few cases to 2° C, ia tempera- 

 ture, 1 mb. in barometric pressure and vapor 

 pressure, and' 10 per cent, in relative humidity. 

 Differences in density are in no case significant. 

 The seasonal means of all elements naturally 

 show better agreement than the monthly means, 

 and the annual means for the shorter and longer 

 period are almost identical. It is thus evident 

 that for the determination .of normal values, par- 

 ticularly those for the months, a longer series of 

 observations is necessary than that upon which 

 the present summary is based. 



Nevertheless, it is deemed satisfactory, for 

 practical purposes, to regard the present means 

 as normals. The author explains further that 

 a longer record is necessary for the northern 

 than for the southern stations, for the winter 

 than for the summer (owing to the greater 

 variability at the colder stations and in the 

 colder season), and at lower than at higher 

 altitudes above the surface. Thus, while 20 to 

 40 years are desirable lengths of record for sur- 

 face data, a much shorter period is necessary 

 for the upper levels. 



To attempt to present in abstract the many 

 striking and interesting features of the 

 numerous diagrams would be impossible, owing 

 to the concise presentation in the original. The 

 large field of information is indicated by the 

 following topics selected from the legends : 

 Seasonal average temperatures, relative humidi- 

 ties, vapor pressures, for each station from 

 the surface to about five kilometers; geograph- 

 ical distribution of mean summer and winter 

 and annual barometric pressures, tempera- 

 tures, relative humidity, vapor pressure, den- 

 sity and resultant winds; means seasonal wind 

 velocities and the percentage frequency of dif- 

 ferent wind directions. All of these dalta ex- 

 tend from the surface to levels three to five 

 kilometers aibove sea-level. 



The study of aerologieal data is two-fold, 

 embracing average conditions and current data. 

 This publicaition from the Aerologieal Division 

 of the Weather Bureau forms an admirable 

 contribution to the former field. Such con- 

 tributions form a setting for the studj' of cur- 

 rent data. But, in spite of the resounding 

 challenge of the upper air to the forecaster, 

 the adequate and complete application of cur- 

 rent aerologieal data must await the extension 

 and amplification of the aerologieal reseau. 

 ■C. LeRoy Meisingee 



Washington, D. C. 



SPECIAL ARTICLES 



DEFICIENCY OF ATMOSPHERIC DUST IN 

 COAL 



In connection with studies in eolian sedi- 

 mentation the writer recently has become inter- 

 ested in an apparent discrepancy among (1) 

 the rate of deposition of atmospheric dust, (2) 



