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SCIENCE 



[N. S. Vol. XXXni. No. 853 



in intensity as we pass from either end towards 

 the middle of the group, and we may depict the 

 relation of the two groups by drawing the 

 enveloping curve for the region of absorption 

 and for that of fluorescence and showing the 

 extent to which they overlap, as in Fig. 4. 

 While detailed quantitative studies of the ab- 

 sorption bands have not yet been made, the 

 preliminary observations indicate that the 

 enveloping curve is an " image " of that of the 

 group of fluorescence bands, just as the broad 

 absorption band of resorufin and other fluo- 

 rescent substances has already been shown" 

 to be the overlapping image of the correspond- 

 ing fluorescence band. 



Fig. 4. Diagram showing the overlapping of 

 fluorescence and absorption in the case of a uranyl 

 salt. 



IsTot only is the envelope of the fluorescence 

 group of the same type as the curve of distri- 

 bution of energy in ordinary fluorescence 

 bands, but each component, as has been shovm 

 by spectrophotometric measurements, has a 

 similar distribution of energy. Moreover, both 

 curves have the same characteristics, although 

 with very different scales of wave-leng-th, as 

 the energy curve of the temperature radiation 

 of a black body. That the relation between 

 the luminescence of solids and liquids and 

 that of vapors is an intimate one is strongly 

 suggested by the comparison of the diagram 

 from Steubing's measurements of the fluores- 

 cence of oxygen (Fig. 1) with the curves for 

 ■the uranyl salts just described, and this sug- 

 gestion is strengthened by the inspection of 



"Nichols and Merritt, Fhysical Review, Vol. 

 XXXI., p. 376. 



Wood's curves for the fluorescence of so- 

 dium vapor. Moreover, the family resem- 

 blance of all these related cases of banded 

 fluorescence spectra to the banded spectra of 

 gases as we find them described in the papers 

 of Deslandres and of Kayser and Runge is 

 unmistakable. In view of these numerous 

 indications of a common property may we not 

 anticipate the attainment of some broader 

 generalization concerning the various types of 

 radiation than has hitherto been made? 



E. L. Nichols 



NOTES ON THE PBELIMINABY BEPOBT OF 



THE COMMITTEE ON THE TEACHING 



OF MATHEMATICS TO STUDENTS 



OF ENGINEERING 



At the meeting of the Society for the Pro- 

 motion of Engineering Education held at 

 Madison, Wis., in June, 1910, the members 

 present were handed sets of galley proofs of 

 the Preliminary Report of the Committee on 

 the Teaching of Mathematics to Students of 

 Engineering, which committee was appointed 

 at a joint meeting of the American Mathe- 

 matical Society and Sections A and D of the 

 American Association for the Advancement of 

 Science in December, 1907. The committee 

 consists of twenty members, ten of them being 

 professors of mathematics, three presidents of 

 technical institutions and seven professors of 

 engineering and consulting engineers. 



The report being only a preliminary one, it 

 is subject to amendment before being pre- 

 sented as a final report, and no doubt the 

 members of the committee will be glad to 

 receive any suggestions which will tend to 

 make the report more useful and more accept- 

 able to engineering teachers. The writer ac- 

 knowledges the great value of the report as a 

 whole, but he has some criticisms to offer on 

 one portion of it, viz., elementary dynamics, 

 which he hopes will be carefully considered 

 by the members of the committee and by 

 others interested, who may be led by it to offer 

 the committee additional suggestions. 



In the preface to the report it is said: 



The defects in the mathematical training of the 

 student of engineering appear to be largely in 

 knowledge and grasp of fundamental principles, 



