July 5, 1901.] 



SCIENCE. 



31 



fundamental a role was assigned, two (the red 

 and the green) did not exist at all so far as 

 known, and one existed only in a wholly erro- 

 neous color, and, moreover, in the fovea where 

 vision is most acute, not even the visual yel- 

 low, the sole carrier of so large an assumption, 

 has ever, by the most careful methods, been 

 detected ; it would seem to be far simpler to 

 suppose that the objective color of the absorb- 

 ent medium has nothing to do with the case. 



The proof which was furnished by Konig 

 immediately after the Ebbinghaus theory was 

 proposed that the absorption of the visual 

 purple is exactly what is needed to account for 

 that increment in vision which is gradually ac- 

 quired upon the oncoming of darkness, ren- 

 dered the theory, of course, far more untenable 

 still, and in fact Professor Ebbinghaus himself 

 seems to be no longer inclined to insist upon it. 

 He says {Grundzilge cler Psychologie, I., 261, 

 262): " Ich habe vor einiger Zeit einen Ver- 

 such in dieser Hiusicht gemacht und darauf 

 hingewiesen, dass zwischen der Art, wie die 

 Farbenblinden Gelb und Blau im Spectrum 

 verteilt sehen, und der Lichtabsorption des 

 Sehpurpurs und des Sehgelb (nach der Unter- 

 suchungen Kiihnes) eine aufFelleude Aehn- 

 lichkeit bestehe. Da nun oflfenbar die Be- 

 wusstseinswirkung der optischen Eeize durch 

 eine den Eindriicken entsprechende Absorption 

 der verschiedeuen Lichtstrahlenvermittelt wer- 

 den muss, so nahm ich an, dass eben in dem 

 Sehpurpur die Heringsche Blaugelbsubstanz zu 

 erblicken sei. 



"Ich sehe jedoch davon ab, die an diesen 

 Ausgangspunkt angeschlossenen und zum Teil 

 davon gang unabhangigen Gedanken hier zu 

 wiederholeu, well sich bei genauerer Unter- 

 suchung des Sehpurpurs durch A. Konig meine 

 ihn betreflfende Annahme nur teilweisebestatigt 

 fand. Das Sehgelb allerdings zeigte in dem ein- 

 zigen Falle, in dem es erhalten werden konnte, 

 eine mit der Blauempfindung der Fai'ben- 

 blinden annahernd iibereinstimnende Lichtab- 

 sorption. Die Lichtabsorption des Sehpurpurs 

 selbst dagegen entsprach vielmehr der Ver- 

 teilung der Helligkeiten in dem Dunkelspectrum 

 des normalen Anges, d. h. also auch in dem 

 Spectrum der total Farbeublinden." 



To refrain from reproducing the theory in 



its author's own text-book of psychology is 

 probably to be regarded as tantamount to with- 

 drawing it. 



C. L. Franklin. 



SHORTER ARTICLES. 

 NOVA PERSEI, No. 2. 



An examination of the Draper photographs 

 of the spectra of Nova Persei, No. 2, by Mrs. 

 Fleming, shows that, like other novae, it has 

 been gradually changing into a gaseous nebula. 

 The resemblance to the nebula N. G. C. 3918 is 

 now so close that in a photograph taken on 

 June 19, 1901, no marked difference was noted, 

 except that the nebular line, 5007, is about eight 

 times as bright as H« in the nebula, and only 

 equal to it in the nova. Tlie lines 3869, 3970 

 (H;/), 4102 (HJ), 4341 (H7), 4688, 4862 (H,/3), 

 4950, and 5007, are common to both and, ex- 

 cept the last, have nearly the same relative 

 intensities. Four bright lines between H7 and 

 H/3 appear faintly in the nova and are not pres- 

 ent in the nebula, while one, 4364, is seen in the 

 nebula but not in the nova, perhaps owing to 

 the proximity of H7. 



Edward C. Pickering. 



Harvard College Observatory, 

 Cambridge, Mass., June 25, 1901. 



LIME AND MAC4NESIA IN PLANT PRODUCTION. 



Since 1899, the writer, with Dr. O. Loew, of 

 the Division of Vegetable Physiology and Pa- 

 thology of the U. S. Department of Agriculture, 

 has been carrying on a series of experiments 

 on the relation of lime to magnesia in the 

 growth of plants. Some very interesting re- 

 sults have been attained which are to be pub- 

 lished in a Bulletin of the Division to be issued 

 at an early date. It may be of interest to here 

 set forth a few of those results. 



It is well known that magnesium salts form 

 some of the more noxious alkali soils of the 

 arid regions. In other sections it has been no- 

 ticed that the soils well fertilized, especially 

 with certain crude potash salts, after a time fail 

 to respond to the fertilizers applied and either 

 become sterile or their j)roductive capacity 

 is greatly reduced. This is apparently due to 

 the accumulation of magnesia in the soil, it 

 being present in some potash salts to a great 



