44 ANNALS NEW YORK ACADEMY OF SCIENCES 



would bo reasonable lo restrict the use ol' the word autipleion to tlio 

 melons due to purely dynamical causes and occurring during the pleio- 

 nian years of the equatorial regions. In the present state of our knowl- 

 edge of these variations, however, it is advantageous not to make a dis- 

 tinction between the direct and the mechanieally proxoked pleions and 

 melons. 



The graphic representation on maps of the positive and negative areas 

 of long-range variations of temperature gives the position and extent of 

 the macropleions and macromeions. In connection with thf study of 

 these maps, expressing long-range variations, the following |ii-oblcins have 

 to be taken into consideration : 



1) The existence of periods of a f^iven number of years, as IS, lit, :i."> or 

 some otlier number, having been admitted, it is nt'cessary to vorifj- to what 

 extent the variations of arbitrary selected stations may cliaracterize long-range 

 variations for a given country or. let us say. the (luestion is to know whether 

 macromeions and macropleions appear and disappear i)eriodically. 



2) Having admitted a presumal)ly universal long-range variation, of al)out 

 thirty-five years duration. Briickner has called exceptional regions (Ausnah- 

 megebiete) some continental areas where the departures of lustra-means were 

 oi>I»osite to the admitted variation. If such is the case, we should observe 

 macromeions on these areas corresi)ouding in time and location to macr()i)leioiis 

 of the miiversal variation. The question is whether the maps justify such a 

 hypothesis. 



:{) 1 >iftei-eiit authors. Blanford, Kremser. Lockyer. Ilildebrandsson. Meinar- 

 dus and Mossman among others, have noticed perfectly ch.aracteristic seesaw 

 variations between given localities. In most of these investigations, only 

 seasonal variations have been studied. Supposing, liowever. that there is no 

 regular periodicity in the variations of long duration, we may ask whether 

 there are corresi>onding areas of simultaneous occurrence of the macrochronic 

 I)leions and melons. 



Satisfactory solutions of these three problems would advance verv- 

 greatly our knowledge of the climatic changes. .1 even think that a scien- 

 tific understanding of these changes would elucidate, lo a great extent, 

 some of the ditficulties encountered in the study of these very much more 

 important climatical variations which occurred in prehistoric times and 

 which are studied from the point of view of geological records.^ and also 

 such historical variations as those which, recently, have been most suc- 

 cessfully studied by Ellsworth Huntington. 



Unfortunately, the main difficulty lies in the lack of precision in our 

 meteorological records. In order to discuss the long-range variations of 



* Die Veriinderungen des Klimas scit dem Maximum der letzten Eiszett. XI Intern. 

 Geologen Kongress. Stock lidlni, I'.no. 



