RHYTHMIC NATURE OF CLIMATIC CHANGES 361 



a mantle of soil in arid regions, with the deposition or the erosion of the 

 materials of terraces, and with the formation of lacustrine strands and 

 deposits, and the results produced when lakes retreat from a high stand. 

 Finally, we have a group of characteristics of epochs of climatic change 

 dependent upon the influence exerted upon life. As animal life depends 

 almost entirely on vegetable life, it is enough to speak of vegetal and 

 intervegetal conditions. 



Ehythmic Nature op climatic Changes — Suggestion of nev^^ Terms 



DERIVED FROM THE KhYTHM OF POETRY 



In the preceding summary of the characteristics of the Pleistocene 

 period of climatic changes it is noticeable that all the descriptive terms 

 are in pairs. Diverse as they are in many respects, they all possess this 

 unity. The great, outstanding characteristic of climatic changes, as we 

 Imow them, is their rhythmic quality. This is universal, pertaining to 

 each and all of the activities or results engendered by the swing of climate 

 from one extreme to the other. A series of climatic changes such as that 

 of the Pleistocene is like a line of poetry, or a stanza, in which there is a 

 constant repetition of a certain definite series of accented and unaccented 

 measures. In order to have terms which shall be applicable to all parts 

 of the world, and which shall not run the risk of being misinterpreted 

 because they carry only a local significance, it seems appropriate to adopt 

 into geology three terms used by the Greeks and Eomans to describe the 

 parts of a poetic composition. The words are "strophe," "arsis," and 

 "thesis." They have passed from Latin into English, and are thus de- 

 fined by the Standard Dictionary: 



"Strophe (stro'-fl). A metrical form of ancient lyric poetry in which the 

 rhythmical movements are combined into groups that are repeated one or more 

 times. . . . Strophe means literally 'a turning.' At the end of the strophe 

 we turn and repeat the same conditions. . . . Stanza, under another sym- 

 bol, means the same thing." 



"Ars/.s- (in prosody). The syllable that receives the ictus or stress of voice, 

 as opposed to the thesis ; also the stress itself." 



"Thesis. In modern prosody . . . the unaccented part of a foot; also, 

 the depression of voice in pronouncing the thesis." 



A poetic example will make the matter clear: 



/ / / / 



Still sits the school-house by the road, 

 / / / 



A ragged beggar sunning. 



' f r / 



Around it still the sumachs grow, 



/ / / 



And blackberry vines are running. 



