Nov, 13, 1879] 



NATURE 



33 



of the paragraph had communicated \vi:h myself previously to 

 "rushing into print," he would have received such information 

 as would have prevented him giving publicity to a statement 

 which however literally correct, is errone us in essence; 

 Edward Hull, 

 Director of the Geological Survey 

 of Ireland 

 Geological Survey of Ireland, Dublin, November 6 

 [We were indebted for the note to the courtesy of Mr. 

 Kinahan, of the Geological Survey of Ireland. — Ed.] 



Lunar Ring 

 While experimenting on the actenic power of lunar light on 

 August 30 last (period of full moon), at 9.30 P.M., I obtained, 

 with a minute-and-a-half exposure, a photographic negative of 

 the moon, which shows a distinct and well-defined ring or glory 

 around it which was not visible to the naked eye on looking 

 directly at the moon in a clear and cloudless sly, nor was there 

 any halo on the ground glass of the camera, nor on the lens, a t 

 the time of observation This is a copy of it from the negative. 



I used no clock-work arrangement with the camera, but allowed 

 the moon to traverse the plate, and I have since then taken 

 several photographic observations under various conditions. I 

 have taken the moon in all her phases, with long and short 

 exposures, in clear and cloudless sky, and never could get a ring 

 even faintly defined. I have also heated the camera and screwed 

 the cold lens into it, carried it into a colder atmosphere in order 

 to produce condensation of dew. I have placed two small 

 separate openings in front of the lens ; on one occasion I dusted 

 puff ball spores upon the lens; on another I breathed warm 

 breath upon it, but never got anything but decided burr, which 

 was always densest near the limb of the moon and gradually 

 tapered away towards the circumference like a bright light seen 

 through a thick fog, but no appearance of ring. I have also 

 taken observations when scud was passing rapidly over the 

 moon, when perfect prismatic halos were visible to the naked 

 eye, but no ring was ever impressed on the photographs; nothing 

 more than a haze, such as that produced by breathing on the 

 lens. The next full moon (September 29) was totally obscured, 

 so that I failed to get an observation then ; but last evening 

 (October 29), at 10 p.m., I was fortunate to get one fine, clear 

 exposure of one-and-a-half minute, and was pleased to see a 

 clear and well-defined ring rise up on the plate during develop- 

 ment, similar in every respect to that obtained on August 29, 

 showing clearly that this unusual appearance is dependent upon 

 the position of the moon in her orbit, she being 111 0] 

 when she manifests ring-giving power and shows us a crown. 

 But why is this? What is the cause of this unusual, and, I 

 believe, hitherto undescribed, appearance? Why should this 

 ring be invisible to the naked eye and yet give a luminous im- 

 pression on a photographic plate ? Why should it appear only 

 at full moon period and not at any other pha ; c? Can it have 

 any connection with what Mr. Newall saw round Mar., through 

 his huge telescope? If the moon had an atmosphere similar to 

 that of the earth, and a star of some magnitude were occulted by 

 the moon at that particular time, it is pbssi le that its light in 

 passing through the lunar atmosphere might be refracted so as 

 to show a corona round the moon ; but it is, pretty generally 

 acknowledge I that there is no atmosphere surrounding it, there- 

 fore there can be no refraction. 



It might be that the solar rays in passing through the upper 

 regions of the earth's atmosphere are so defracled.that the ultra- 

 violet rays (though invisible) are thus rendered visible. 



It is also possible that the doubly-reflected lunar light (the 

 ashy light), in passing back to the moon from the earth, en- 

 counters on its passage the reflected solar rays from the moon, 

 arresting and nullifying in proportion to its strength, so much of 

 the light proceeding from the moon thereby causing a clear 

 space around the moon-limb, a region of inertia, while the 

 reflection from the disk of the earth, being larger than the moon's 

 reflecting disk, will show itself as a ring on the cuter edge of 



the neutral zone, much in the same manner as two heliograpbic 

 reflectors would act if they were so arranged as to t 

 respective reflections directly into and upon each other, the one 

 being small and the oilier larger, ju^t as the mo in is the smaller 

 and the earth the larger body, the smaller b< 

 smaller, brighter light, while the larger body would reflect from 

 its broader disk a less brilliant light with a feebler force, yet not 

 so feeble as to prevent it arresting an amount of force equal to 

 itself. George Lerwick 



Sunderland, October 30 



[Dr. Lerwick's explanation appears scare. 

 involves the assumption that a ray of light meeting an ther can 

 arrest it ; and also it involves the visibility of 

 traversing space. We would remark that faint halos due to 

 atmospheric causes are often seen almost masked ly the bright- 

 ness of a full moon, and the photograph being 1 

 far as the moon is concerned, does not show the relative actinic 

 brightness of moon and halo. Would Dr. Berwick try further 

 experiments with shorter exposures, and also ascertain from a 

 number of photographs how far on either side of full moon a 

 halo can be photographed, and whether it is always present 

 during similar periods ? — Ed.] 



Phosphorescence 



A few days ago my attention was draw n to the phosphorescence 

 of some fish (haddock) just received from the coast. The light 

 was most brilliant about the fins and in-ide of the fish, which had 

 been gutted. A spectroscope of low dispersive poa er showed all 

 the light to belong to the green part of the spectrum. Approxi- 

 mate measures gave 557 "5 (mm.) and 4SS'4 as_the extre 

 lengths, the part from 557-5 to 503^4 being somewhat brighter 

 than the remainder, with a feebly indicated maximum at 527'6. 



In the hope of getting a brighter spectrum 

 washed in as small a quantity of water as possible, 'i his water 

 became highly phosphorescent, and when agitated in a bowl, 

 gave beautiful luminous caustics, but neither in the bowl nor in 

 a glass trough, nor in a tube of half-inch bore, did (lie liquid give 

 a brighter spectrum than that afforded by the fish. 



A large bubble of air was inclosed with the liquid in the tube. 

 When the tube was violently agitated, it became luminous from 

 end to end ; if then held vertically, the light rapidly faded except 

 near the top of the liquid, but on suddenly inverting the tube, the 

 bubble of air slowly ascended, causing the whole contents of the 

 tube to phosphoresce very brilliantly. This was a most striking 

 phenomenon. After the lapse of some nine hours, the liquid 

 had almost entirely lost the power of giving light. 



The Observatory, Dunecht, Aberdeen, Nov. 



Ralph Cuieland 



The " False Dawn" 



For some time past certain considerations had led me 

 gradually to infer that the " Fa'se I 'awn " of the very extensive 

 literature of Islam, whether Arabic, Persian, or Tin 

 and whether prose or verse, is another name foi 

 Light." No dictionary yet published so explaii 



1 submitted my idea, and reasons to a MI 

 foreign astronomers and linguists. All exprc 

 currence in those views ; but direct proof of their c 

 was not at once forthcoming. Recently, however, ti 

 kindness of the Hydri grapher to the Admiralty, 

 effort was made to s„!ve this question by Capt. Wharton, 

 commanding II. M.S. Fawn, now cruising in th 

 Marmora. The method employed by that officer, and its 

 conclusive result, cannot be better described than by giving his 

 own words as follows : — 



II. M.S. Fawn, Tuil 



September 26, 1S79 



Dear Capt. Evans, 



For the information of Mr. Redhoue, I have to tell 

 you that I can satisfactorily answer his question 

 dawn of the Turks. 



On the morning of the 20th instant, at 3.30 A.M., I went to a 

 mosque at Luyukdere, and interviewed the Imauiri, who, on 

 being asked for the "fejri kyazib," 1 at once pointed out the 

 zodiacal light, then brightly shining in the east. . . . There can 

 be no doubt as to the coincidence of the two. 



Yours sincerely, 



W. J. I, Wharton 



1 " Fejri Ky.lziL " is the Aral.:.. . 1 ressj n for " the false dsivn." 



