436 



SCIENCE 



[N. S. Vol. XLTI. No. 1192 



chapter on eleetroinagnetic waves under the 

 head of "Electricity," in which the nature 

 and chief properties of these waves and their 

 application in wireless telegraphy are briefly 

 discussed, paves the way for a more thorough- 

 going discussion of these waves under the 

 head of " Light." From the beginning of 

 his study of light to the end the student 

 should never be allowed to lose sight of the 

 fact that light is essentially an electromag- 

 netic phenomenon; each branch of the subject 

 should be developed on the basis of this 

 theory; and the intimate relationship between 

 the optical properties of a body and its elec- 

 trical properties should be constantly stressed. 



There is perhaps no other branch of sci- 

 ence in which the disparity between the point 

 of view of the investigator and that of the 

 elementary student is quite so great as in 

 optics. The modem worker in this field 

 thinks of the phenomena of light in terms 

 of electromagnetic waves and the behavior of 

 electrons under the influence of these waves; 

 to the student, on the other hand, the ideas 

 which form the working basis of the investi- 

 gator in his researches are meaningless, be- 

 cause he has no knowledge of the theory 

 upon which these depend or of the experi- 

 mental facts which underlie them. It must 

 be admitted that in all essentials the subject 

 of light is taught to-day very much as it was 

 taught fifty years ago; exactly as we might 

 expect it to be taught if Maxwell had never 

 lived and if the theory which we owe to him 

 had never been suggested. It is to be sin- 

 cerely hoped that the near future may witness 

 a radical change in this respect, and that 

 those principles which serve as the ground- 

 work of the modern physicist and which 

 guide him in his researches may be corre- 

 spondingly stressed in our attempts to pre- 

 sent the essential facts of optics to the 

 student. 



David Vance Guthrie 



Louisiana State XlNrvEESiiY 



TRANS-PACIFIC AGRICULTURE 



Whate'^'ER the merits of the particular case, 

 the coincidence between the design called 



House of Teuhu in Arizona and the Minoan 

 Labyrinth in Crete, described in Science for 

 June 29, page 677, is of interest as an illus- 

 tration of a large class of facts in need of 

 the more general scientific consideration that 

 Professor Colton bespeaks. The statement, 

 " There are three possible explanations of the 

 coincidence," needs to be extended. Ameri- 

 can origin and prehistoric transportation to 

 the old world is a fourth possibility as worthy 

 of consideration as pre-Columbian transfer 

 from the old world to America, introduction 

 with the Spanish conquest, or independent 

 origins in the two hemispheres. 



Several cultivated plants of American 

 origin appear to have been carried across the 

 Pacific in prehistoric times, such as the coco- 

 nut palm, the sweet potato, the bottle gourd, 

 the yam bean, and the Upland species of 

 cotton. The same name for sweet potato, 

 cumara or humara, is used by the Indians of 

 the Urubamba valley of southern Peru and 

 by the Polynesians, and other plant names are 

 similar. Moreover, since the migrations of 

 the prehistoric Polynesians extended across 

 the Pacific and Indian Oceans, from Hawaii 

 and Easter Island to New Zealand and Mada- 

 gascar, it is not unreasonable to look for 

 traces of communication with ancient Amer- 

 ica in the early civilizations of Asia, Africa 

 or the Mediterannean region. 



Agriculture is the primary, fundamental 

 art of civilization, and the evidence of the 

 cultivated plants is the most concrete of any 

 that bears upon the question of prehistoric 

 communication between the more civilized 

 peoples of the two hemispheres. No such 

 significance can be ascribed to the contacts 

 or migrations of non-agricultural people 

 across Bering Strait or the Aleutian Islands. 

 Por ethnologists, it may be easy to assume 

 that agriculture had separate beginnings in 

 the old world and the new, but botanists are 

 unable to believe that the same genera and 

 species of cultivated plants originated inde- 

 pendently in the two hemispheres, or that they 

 were carried across the Pacific without human 

 assistance. 



Peru imdoubtedly was the chief center of 



