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SCIENCE 



[N. S. Vol. XLVI. No. 1192 



than weaken tlie general thesis that bacteria 

 represent a very ancient form of life, for the 

 denitrifying bacteria are generally conceded to 

 be higher in the scale of bacterial life than 

 either the nitrogen fixers or the nitrifiers. If 

 organisms related to the higher denitrifiers ex- 

 isted in the Algonkian, is it not reasonable to 

 assume that simpler forms existed earlier in 

 geologic time? In other words, the hypothet- 

 ical point as to whether the Algonkian bac- 

 teria represent forms related to the nitrifiers 

 or the denitrifiers is immaterial to the conclu- 

 sion regarding the great antiquity of bacteria. 

 As to the matter of " popular science " in 

 general the popularizer always runs into 

 danger as soon as he leaves his own special 

 field of research. 'So one is more conscious of 

 such pitfalls than myself ; it is difficult enough 

 to avoid pitfalls in one's own field without 

 venturing into others. At the same time I feel 

 very strongly that little or no progress will be 

 made in the principles of biology (as distin- 

 guished from discoveries in special fields of re- 

 search) unless biologists have the courage to 

 venture occasionally into the fields of physics, 

 chemistry, physiology and zoology in order to 

 look at life from a broader and more distant 

 point of view. Such an attempt I have made 

 in the Hale Lectures which Dr. Breed cites 

 and which now appear in a somewhat more 

 carefully considered form in " The Origin 

 and Evolution of Life." On every topic I 

 have sought and found the cooperation and 

 criticism of other workers — in physics of 

 Pupin, in chemistry of Gries and Clarke, in 

 zoology of Wilson, in astronomy of Hale and 

 Eussell, in botany of Goodspeed and Howe, 

 and many others. Although every effort has 

 been made to guard against errors, it may be 

 that others have slipped in, but I take it for 

 granted that specialists will not mistake a 

 popular work for a work of reference nor 

 imagine that I presume to speak with the au- 

 thority of a specialist in any field but my own. 



Henry Fairfield Osborn 



the teaching of optics 

 The recent discussion in the columns of 

 Science as to the best method to be followed 



in presenting the fundamental laws and con- 

 cepts of mechanics to the student has been 

 followed with much interest by teachers of 

 physics. To the writer it seems equally im- 

 portant that attention be directed to another 

 branch of physics, and the question raised 

 as to whether there should not be a radical 

 change in our methods of introducing the stu- 

 dent to the subject of optics. 



It is generally conceded by those qualified 

 to speak with authority that the establish- 

 ment of the electromagnetic theory of light 

 represents one of the greatest achievements 

 of modern science. Yet in spite of the far- 

 reaching importance of thie principle, the 

 average student who has completed his col- 

 lege course in general physics, or even in 

 many cases more advanced special courses, is 

 entirely unfamiliar with the meaning or the 

 significance of the electromagnetic theory. 

 This need occasion no surprise, however, in 

 view of the methods commonly employed at 

 present in teaching the subject of optics. For 

 certainly a text-book which either does not 

 mention the electromagnetic theory of light 

 or relegates it to a footnote or inconspicuous 

 paragraph is hardly calculated to inspire the 

 student with any great respect for that 

 theory. This criticism applies, not to our 

 text-books alone, but with equal force to the 

 ordinary lecture course. 



In order to investigate the justice of this 

 claim that one of the most important prin- 

 ciples of modern physics is almost entirely 

 ignored in our present system of teaching 

 and is seldom accorded the attention its im- 

 portance demands, the writer recently made 

 a careful examination of ten representative 

 text-books of physics, all of them published 

 within the past decade and including prac- 

 tically all, so far as knovni to the writer, 

 which are very extensively used in our Amer- 

 ican colleges and universities at the present 

 time. As a result of this examination it 

 was found that in three of these text-books 

 no reference whatever is made to the electro- 

 magnetic theory; three other authors content 

 themselves with a bare mention of the theory; 



