374 SCIENTIFIC RECORD FOR 1884. 



diction for this year; in fixct, lie had observed that the blue was even 

 less prominent than in 1883, that the green was more prominent, and 

 that even violet occasionally occurred. Montigny suggests that the 

 blue tint in the scintillation is due to the water in the atmosi^here, which 

 is known to have a bluish tint when viewed by ordinary sunlight. 

 [Z. 0. G. 3[., XIX, p. 534.) 



371. L. Thollon contributes to the Bulletin Astronomique an elabo- 

 rate study into the structure and origin of the lines forming the group 

 B of the solar spectrum, which paper is handsomely reproduced in N'<i- 

 ture, XXX, j). 520. This region was carefully worked over by Piazzi 

 Smyth, and Langley ; but Thollon has now revised his own previous 

 work, and the elegant map given by him show^s at a glance, first, the 

 metallic lines ; second, those produced bj' atmospheric vapors — probably 

 the aqueous vapors ; third, those produced by atmospheric gases — oxy- 

 gen, nitrogen, carbonic acid, and any others that do not materially vary 

 in quantity, leaving finally non-telluric lines, twenty-five in all, or sev- 

 enteen if w^e count double and triple lines as one. The lines due to at- 

 mospheric gases constitute a sj'stem of twelve pairs, and tlie whole 

 group is distinguished by its regular symmetry. Under such a scru- 

 tiny as this there seems no doubt that certain lines are also a perfect in- 

 dication of the hygroraetric state of the air. In 1882 Professor Egoroft', 

 of Warsaw, joined Thollon in his investigations at Paris, where they 

 examined the spectrum of a beam of electric light 10 kilometers long, 

 and which gave a perfect reproduction of the telluric rays ; afterwards, by 

 condensing oxygen in a short tube, the gaseous rays were obtained fojj the 

 groups A and B, and probably a greaterquantity of oxygen would have 

 given the feebler group Alpha; so that these three groups. A, B, and 

 Alpha, originate in theabsorption of atmospheric oxygen. That the spec- 

 trum of absorption for cold oxygen should differ so much from the spec- 

 trum of emission for incandescent oxygen is, he thinks, attributable to 

 the influence of heat. Thollon is at present engaged in the further 

 search for lines or groups due to the presence of nitrogen or carbonic 

 oxide. Hitherto, apart from the oxygen, or A, B, and Alpha groups, 

 he has discovered no lines that may be confidently attributed to the 

 constant gaseous portions of the atmosphere. {Nature, xxx, p. 520.) 



372. G. Pizzighelli publishes, through Dr. E. Hornig, a work on Acti- 

 nometry, or the photometry of the chemically active radiations. The 

 author is a most expert photographer, and has here compiled an almost 

 exhaustive account of modern apparatus and methods for measuring the 

 intensity of light by photographic and chemical methods. He gives a 

 special chapter to the meteorological applications of actinometry, espe- 

 cially the results of the studies of Pernter, published in 1882. {D. M. Z., 

 I, p.'420.) 



373. Captain Abney, as the result of photographing the ultra-red 

 portion of the solar spectrum in very various atmospheric conditions, 

 found that in very dry weather the photographs show only absorption 



