428 



SCIENCE 



[N. S. Vol. XXXI. No. 794 



partment of agriculture, if this information 

 were only coordinated according to the needs 

 of such a research. 



Secondly, to find and then to solve, one by 

 one, the problems of dynamical climatology. 



Working along this line and leaving aside, 

 for the present, the continuation of my study 

 on modes of formation and progressive dis- 

 placements of the thermopleions and anti- 

 pleions,' this study being extremely difficult, I 

 found simpler and more fundamental phe- 

 nomena by drawing maps of the annual de- 

 partures of atmospheric pressure. 



These maps led me indeed to most unex- 

 pected conclusions. 



Considering the data of the tables of " baro- 

 metric pressure " of Sir Norman Lockyer, and 

 utilizing the departures given in Bigelow's 

 report on atmospheric pressure, as well as 

 those published in the annual summaries of 

 the Monthly Weather Review, I drew curves 

 showing the geographical distribution of 

 equal departures. 



I found that, with few exceptions, the areas 

 of positive and negative departures displace 

 themselves from east to west, from the At- 

 lantic across America toward the Pacific. 

 In reality, however, the movements of the 

 areas of hypo- and hyper-pressure are very 

 complicated, there being generally two dis- 

 tinct directions of propagation simultane- 

 ously apparent. Some maps show clearly the 

 existence of intercrossing waves coming from 

 beyond the northeast and southeast of the 

 United States. 



These waves are extraordinary because of 

 their slow progress. To verify the fact that 

 waves of hyper- and hypo-pressure of the map 

 of a given year are really those of the preced- 

 ing year displaced westward, I have calcu- 

 lated consecutive annual means. 



The diagrams of these figures — ^for stations 

 situated along the presumed path of a center 

 of too low or too high annual pressure — show 

 that it is really with a wave movement, of a 

 particular kind, that we have to deal. 



I shall not dwell on the details, this being but 



' Arctowski, " L'enchalnement des variations 

 climatiques," Bruxelles, 1909. 



a preliminary notice of a paper which wiU be 

 published in the Bulletin of the American 

 Geographical Society. I must state, however, 

 that my method of utilizing consecutive 

 means, which makes it possible to draw yearly 

 maps from month to month, will enable me 

 to foresee the changes which will occur. 



To know how far this method may be ap- 

 plied to forecast seasonal distribution of pres- 

 sure, I must first investigate the yearly varia- 

 tions of pressure, and calculate the consecu- 

 tive means of many series of observations, to 

 find out if there is not a periodicity in the 

 long-range atmospheric waves. 



From the discussion of annual maps it ap- 

 pears most probable that the amplitudes of 

 those waves increase and decrease in harmony 

 with the sun-cycle of about eleven years. 



Henryk Arctowski 



New York 



COLLEGIATE INSTRUCTION 

 The Committee on College Instruction of 

 Section L, of the American Association, re- 

 cently ordered the publication, if practicable, 

 of certain samples of the facts obtained in a 

 study of (1) the size of classes (a " class " 

 being defined as a group of students dependent 

 upon one teacher for instruction in a course) 

 and of (2) the actual work done by individual 

 students in fulfilment of the requirements for 

 the A.B. degree. By the courtesy of the editor 

 of Science, these facts are now printed. 



Size of Classes 

 In almost all colleges that report the condi- 

 tions of instruction in this particular, there is 

 an enormous variability in the size of the 

 groups taught by a single teacher in under- 

 graduate courses. Within the same institu- 

 tion the number will commonly range from 

 three or even fewer to a number equal to a 

 fifth of the entire student body. The facts in 

 this regard have been reported, though not 

 every year, and not without many ambiguities, 

 by Boston University, Bowdoin, Brown, Bryn 

 Mawr, University of California, Harvard, 

 Johns Hopkins, Stanford, Oberlin, Eadcliffe, 

 University of Texas, Tufts, Western Eeserre, 



