402 



NATURE 



{August 21, 1879 



Hudd part 2 of a catalogue of the Lepidoptera of the Bristol 

 district. 



"Science Teaching in Living Nature, a Popular Introduc- 

 tion to the Study of Physiological Chemistry and Sanitary 

 Science," is the title of a little volume by Mr. W. H. Watson, 

 F.C.S., just published by Stanford. 



The additions to the Zoological Society's Gardens during the 

 past week include two Diana Monkeys {Cercopithecus diana) from 

 West Africa, presented by Mr. F. J. Crocker; a Green Monkey 

 {Cercopithecus callitrichus) from West Africa, presented by Mr. 

 C. F. S. Day ; a Malbrouch Monkey (Cercopithecus cynosurus) 

 from West Africa, presented by Miss Agnes Barker ; a Black 

 Stork (Ckoiiia nigra) from Jutland, presented by Prof. J. 

 Reinhardt, F.M.Z.S. ; a Rose-crested Cockatoo (Cacatua 

 moluccensis) from Moluccas, presented by Miss Foster ; fourteen 

 Golden Tench ( Tinea vulgaris, var.), presented by Lord 

 Walsingham, F.Z.S. ; a Common Buzzard (BuUo znilgaris), 

 European, deposited ; two Black-footed Penguins (Spkinisais 

 demcrsus) from South Africa, purchased ; two Crested Pigeons 

 (Oc}phaps lophotcs), two Geoffroy's Doves (Peristcra geoffroii), 

 bred in the Gardens. 



OUR ASTRONOMICAL COLUMN 

 The Elong.^ted Nebulae. — The amateur provided 

 with an equatorial of fair aperture and a parallel-wire 

 micrometer might do good service by the accurate deter- 

 mination of the angles of position of the elongated or 

 greatly-extended nebute, of which so far the number of 

 reliable measures is but small, though such objects are 

 pretty commonly distributed. The necessity for further 

 observations in this direction is well illustrated by the 

 note to No. 2501 of Sir John Herschel's General Catalogue 

 = H. L94; H. made the nebula by one observation ex- 

 tended n. to s., byanothernf. to sp., while two observations 

 by Sir John Herschel agree in making it extended in the 

 parallel ; " Surely," he remarks, " it does not rotate ? " 

 D'Arrest (" Siderum Nebulosorum " ) merely says : " Circa 

 directionem axis nihil annotatum fuit." 



In 1874 Mr. Cleveland Abbe called attention to this 

 subject, and in the American Journal of Science and Arts, 

 January, 1875, has collected the approximate places of 

 about sixty elongated nebute from Herschel's catalogue, 

 and has appended formulse by which the right ascension 

 and declination of the poles of a .rery much extended 

 nebula may be calculated. These formula he has applied 

 to such measures or estimations, often rough ones, of the 

 angles of position as were then published. 



The New Binary Star t Cygni.— This star, the 

 duplicity of which was detected by Mr. A. G. Clark in 

 October, 1874, with the 26-inch object-glass manufactured 

 for Mr. McCormick,' of Chicago, well deserves following 

 up ; in the 3J years to i878'4, when measures were made 

 by Mr. Burnham, the atigle of position had retrograded 

 25 , with but little change of distance, though a slight de- 

 crease may be suspected. The components are about 4*5 

 and 8. Right ascension for 1880, 2ih. lom. 8s. ; declina- 

 tion, 37° 32'. If the motion in angle has been equable 

 since 1874, the position may now be about 140°. 



LETTERS TO THE EDITOR 



[ lilt Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, or 

 to correspond with the writers of, rejected manuscripts. No 

 notice is taken of anonymous communications. 

 [ The Editor urgently requests correspondents to keep their letters as 

 short as possible. 7 he pressure on his space is so great that it 

 is impossible othenvise to ensure the appearance even op com- 

 munications containing interesting and novel /cuts.'] 

 "Report of an Unusual Phenomenon Observed at Sea" 

 As the unusual phenomena observed in the Persian Gulf, de- 

 scribed in Nature, vol. xx. p. 291, has hitherto called forth no 



remarks, I venture to put forward a suggestion that may be of 

 service in elucidating the matter. 



First, I would observe that the so-called parallel waves were 

 probably arcs of large concentric circles, whose common centre 

 lay south-south-west of H.M.S. Vulture's first, and east of her 

 last, position. The distance between these positions was about 

 a knot and a half, therefore the vessel was never nearer this 

 centre than about half a mile, and a short arc of a circle of thi:; 

 radius might well be deemed straight. 



The accompanying diagram, drawn from the data, shows 

 the position of the centre of disturbance, and of the luminous 

 waves, with relation to the course of the ship, taking the above 

 view, which I think is borne out by the character of the second 

 series of luminous wavesthrough which H.M.S. f^«//«r<; passed 



Most living creatures possessing phosphorescence have moii 



'■k9 ' 



i 



Scale I7 uil Naut mile 

 Diagram showing 'position, of huninevts v/cn't cenires 



or less control over its display. In the case of the fire-fly, tli 

 light that one emits calls forth almost instantaneously answeriii-- 

 flashes from others. No dweller in the tropics can have faileJ 

 to observe the manner in which trees are lit up by the simultan- 

 eous flash of thousands of fire-flies, and the period of darkness 

 that intervenes before the next flash. If then we consider the 

 Vulture to have passed through a shoal (if I may so term it) of 

 auimalcula:, possessing the power of exhibiting phosphorescence 

 intermittently, and exciting each other to do so, the impulse 

 travelling from one to another at the rate of 125 feet a second, 

 and the display of light to the dark interval bearing the ratio 

 I to 3 (in time, \ of a second to f ), Me have accounted for the 

 phenomena so far as the luminous waves are concerned. 



What were the central disturbances that originated the action, 

 it is impossible to say, though it is easy to imagine several cause) 



of irritation, that would not have been detected by the simple 

 observations taken on board the vessel. 



The luminous ■ waves of the smaller series "meeting the 

 parallel waves from south-east did not cross, but appeared to 

 obliterate each other at the moving point of contact." The 

 .above is difficult to explain, if the luminosity of the waves was 

 obliterated at the actual intersections. It can however be readily 

 shown that close to the intersections are spaces where the phos- 

 phorescence of the animalcula; would have to be displayed for 

 twice as long a period as in other positions, and we have but to 

 admit a want of energy to meet this call, and dark spaces will 

 appear in each system of waves, immediately following the 

 passage of the crossing wave. 



This would certainly give the appearance of one wave 

 obliterating the other. 



