468 



NATURE 



[September 6, 1S94 



Charpenlier states that, nnder favonrable conditions, he has 

 been able to detect the existence of a second, and even of a third, 

 dark band of greatly diminished intensity, though he adds that 

 the observation is a verj- difficult one. What is probably the 

 same effect in a different form can, however, be shown quite 

 easily in the following manner : — 



In a blackened zinc disk 15 cm. in diameter, there were cut 

 two opposite radial slits, about 05 mm. in width. The disk 

 was rotated at the rate of one turn per second in front of a 

 sheet of ground glass, behind which was an incandescent lamp. 

 The ylass was covered with opaque paper, in which a circular 

 opening was made of slightly less diameter than the disk. The 

 disk was placed opposite this opening, and no light reached the 

 eye except such as passed through the two slits. When the 

 disk was observed from a distance of about I \ metres, the eye 

 being tixed upon its centre, each slit appeared to give four (or 

 possibly five) luminous images, arranged like the ribs of a partly 

 opened fan. The images were distinctly separated by dark 

 intervals near the circumference, but overlapped one another 

 towards the centre. The leading image was naturally the 

 brightest, each consecutive image being considerably weaker 

 than its precursor. AH had the same tone of colour, namely, 

 that of the yellowish-light given by the electric lamp. The 

 usual blue recurrent image could also be seen following the 

 images of the radial slits, at an angle of about 80°. 



It appears, then, that when the retina is exposed to the action 

 of light for a limited time, the complete order of visual 

 phenomena is as follows : — 



(1) Immediately upon the impact of the light there is 

 experienced a sensation of luminosity, the intensity of which 

 increases for about one-sixtieth of a second : more rapidly 

 towards the end of that period than at first. 



(2) Then ensues a sudden reaction, lasting also for about one- 

 sixlieth of a second, in virtue of which the retina becomes 

 partially insensible to renewed or continued luminous impres- 

 sions. These two effects may be repeated in a diminished 

 degree, as often as three or four times. 



(3) The stage of fluctualiin is succeeded by a sensation of 

 steady luminosity, the intensity of which is, however, consider- 

 ably below the mean of that experienced during the first one- 

 sixtieth of a second. 



(4) After the external light ha> been shut off, a sensation of 

 diminishing luminosity continues for a short time, and is suc- 

 ceeded by a brief interval of darkness. 



(5) Then follows a sudden and clearly-defined sensation of 

 what may be called abnormal darkness — darker than common 

 darkness — which lasts for about one-sixlieth of a second, and is 

 followed by another interval of ordinary darkness. 



(6) Finally, in about a fifth of a second after the extinction of 

 the external light, there occurs another transient impression of 

 luminosity, generally violet coloured, after which the uniformity 

 of the darkness remains undisturbed. 



No account has been taken of the comparatively feeble after- 

 image, to which the phosphorescent trail before referred to is 

 due, and which may last for two seconds or more. 



In an addendum to the paper reference is made to the recent 

 experiments of Dr. Carl Hess (" Pflugei's Archiv fiir Physio- 

 logic," vol. xlix. p. 190). 



Paris. 



Academy of Sciences, August 27. — M. Lrcwy in the 

 chair. — On the variations of the apparent signs of lines and 

 angles, in direct vision and in vision by movements of the eyes 

 and head, by M. Ch. Henry. Formula and tables are given 

 embodying the results of the consideration of a great number of 

 ca%es and enabling apparent sizes to be calculated. — On the 

 transformation of {ijuatioiis canoniijiiet in the problem of three 

 bodies, by M. Paul Vernier. — On the possibility of rcpl.icing 

 the indeterminate problem given by the generalisation of Pascal's 

 theorem by a deicrmin.iie problem, by M. Paul Serret. — -Ke- 

 searches on the movements of the solar atmosphere, by M. H. 

 Deslandres. An examination of many photographs of spectra 

 of the sun reveals interesting phenomena in connection with a 

 bright line occuning within the wide dark lines H and K of 

 calcium. This line may be resolved into two bright lines 

 enclosing a dark line; the bright lines correspond to the lower 

 layers of the chromosphere, while the dark line belongs to the 

 higher layers. These bright lines often show dissymmetry, some- 

 times one and sometimes the other becoming the narrower. 

 Spectra of the facui.e do not usually show this dissymmetry, but 

 it ii a common condition over the remainder of the surface, and 



NO. 1297, VOL. 50] 



is more pionounced near the equator than in theneighbourhood 

 of the poles. Near spots the observed dissymmetry is often in 

 the opposite direction on opposite sides, and the narrowing of 

 the line is sometimes irregular. These phenomena can be ex- 

 plained on the hypothesis of a continual circulation of the sun's 

 atmosphere, but it is worth noting that a less marked dissym- 

 metry has been obtained in the calcium spectrum produced by 

 the induction spark. Resemblances are pointed out between 

 these phenomena and those observed in the spectrum of Nova 

 Aurigie. — A remarkable thunderstorm, by M. Ch. V. Zenger. 



BOOKS, PAMPHLETS, and SERIALS RECEIVED. 



Books. — Fabrication lic la Feme: E. dc Billy (Paris, ("..luihier-VilLirs). 

 — City and Guilds of London Insiiiuie, Programme of Technological 

 Examinations, &c.. Session 1S94-9S (^Vhittakcr). — Review of Mineral Pro- 

 duction in India for 181)3 (Calcutta^. — Sach-imd Oris-Verxeichnis zu den 

 Mineralogischcn und Geol Kischcn Arbcitcn von Gerhard vom Rath ; W. 

 Bruhns and K. Bu.sz (Lcipzic, Engclmann). — Kaialog der Bibliothek der 

 Kaiscrlichen LeopoldiniscnCaiolin-schcn Deutschen Akademie der Natur- 

 forscher, Fiinfte Liefg. Band 22 : O. Grullch (Halle, Blochmatui).— The 

 Country Month by Months September, Owen and Boulger (Bliss). 



Pamphlets. — Tellustria: B. G. Jenkins (Norwood, Morgan) — Man- 

 chester Microscopical Society Transactions and Annual Report, 1893 (Man- 

 chester). 



Serials.— Zcitschrift fiir Witsenschafiliche Zoologie, Iviii. Band, i and 2 

 Heft (Leipzig, Engclmann). — Natural History of Plants. Part 5: Kcmer 

 and (.Jliver (Blackie). — Contemporary Review, September (Isbistcr). — 

 Scribner's Magazine, September (S. Low). — Journal of the Chemical 

 Society, September (Gumey). — National Review, September (Allen). — 

 lournal of the Asiatic Society of Bengal. Vol- Ixiii. Part a, No. i : Part ■?, 

 No. I (C.-ilcutia).— Himmcl und Erdc, September (Berlin). — Fortnightly 

 Review. September (Chapman). 



CONTENTS. PAGE 



A NeoLamarckian Theory of Evolution. l>y E. 



B. P 445 



Celestial Photographs. By Dr. A. A.Common.F.R.S. 447 

 Deaf-mutism. By P. Macleod Yearsley, F.R.C.S. . 449 

 Our Book Shelf:— 



Ilamniarslcn : " A Text-book of Physiological Che- 

 mistry " 449 



Chrystal : "Electricity, Electrometer, Magnetism, 

 and Electrolysis." — Dr. James L. Howard . . 450 

 Letters to the Editor : — 



On the Velocity of the Constantinople Earthquake- 

 Pulsations of July 10, 1S94. — Charles Davison . 450 

 Photo-electric Phenomena.— Drs. J. Elster.indH. 



Geitel 451 



A Remarkable Meteor. {///nstra/eJ.)—Jobn W. 



Earle 452 



A New Rhynchobdellid. — Dr. John Young .... 452 



The Bleaching of Beeswax. — J. S. D 452 



Sunshine and Water-Microbes. By Mrs. Percy 



Frankland 452 



Notes 454 



Our Astronomical Column : — 



Recent Observ.ations of Mars • . . 457 



The Mass of Jupiter 45^ 



American Association for the Advancement of 



Science. I'.y Dr. Wm. H. Hale 45* 



The Iron and Steel Institute 459 



Physiology at the British Association 460 



British Association Conferences of the Delegates of 



the Corresponding Societies 464 



Scientific Serials 4^6 



Societies and Academies 4^6 



Books, Pamphlets, and Serials Received 468 



