204 



KNOWLEDGE. 



[September, 1901. 



appears to be continuous; at least with the means at 

 our disposal we have been unable to detect any bright 

 lines." 



Elements of the comet have been computed by 

 H. Thiele, of Bambers; (.-1.^/. J'lcJi. 3731), from observa- 

 tions on April 24 (Ca^pe Town), May 2 (Windsor), and 

 May 15 (Mount Hamilton), and they are as follows: — 

 P.P. = 1901, April 24-28824, M.T., Berlin. 

 CO = 203° 1' 15"-8. 

 n = 109- 44' i"-o. 

 ; = 131° 1' 7"'.i. 

 Log. 2 = 9 38804G. 

 The perihelion distance was nearly 23 millions of miles, 

 so that this comet did not, like the great southern 

 comets of February, 1880, and January 1887, pass very 

 close to the sun. 



The astronomical discoveries that will be made during 

 the present century will undoubtedly be very numerous 

 and some of them" brilliant, but it will be difficult for 

 it to furnish a parallel ix> the first few months of its 

 opening year with its brilliant star and its great comet. 



Hcttcrs. 



[The Editors do uot hold themselves responsible for the opiuious 

 or statements of correspondents.] 



NOVA PERSEI. 



TO THE EDITORS OF KNOWLEDGE. 



Sirs, — With reference to the photographs of the Nova 

 Persei region in the July number of Knowledge, my 

 attention has been kindly called independently by two 

 of your readers, Mr. ,T. E. Davidson and Mr. J. E. Gore, 

 to what is apjjarently a bright star visible on the photo- 

 graph of Feb. 28, but absent from that of Feb. 20. It 

 will be readily found at a short distance south-east of 

 the bright star 36 Pei^sei, visible near the upper (north) 

 part of the, photograph. Reference to the original 

 negative shows, however, that this object is not the 

 image of a real star, but is due to a spot on the film ; 

 and it is absent from another photograph taken upon 

 the same night. 



Now that Perseus is coming round into a favourable 

 and convenient position for evening observation, no 

 doubt many observers will contemplate looking up the 

 Nova, and hence it may be of interest to state that the 

 star is still a fairly bright object. On several occasions 

 lately it has appeared between 6 and dh magnitude ; 

 and on the nights of the 9th and 10th August, it was 

 plainly visible in an opera-gla.ss. The intense red colour 

 formerly characterising the object seems, however, to 

 have almost entirely disappeared, 



A, Stanley Williams. 

 Brighton, 1901, Aua. 12, 



DOUBLK KAJNMOW. 



TO THE EUlTOHb OF KNOWLKDCL 



Sirs, — Whilst staying at the Goschenen Alp in July 

 last a thunder-stoiin accompanied by heavy rain passed 

 overhead one afternoon about 5 o'clock. It was not of 

 long duration, and the sun soon shone out brightly from 

 below the western margin of the storm clouds, whilst 

 the rain was still falling copiously at the eastern end 

 of the valley. On this rain a double rainbow of con- 

 siderable brilliancy was produced and ])crsis(cd for ,')-10 



minutes. Not remembering to have seen a similar 

 phenomenon, I venture to mention it to the readers of 

 Knowledge and to ask for some suggestion as to the 

 probable cause. This was not an ordinary case of a 

 primary and secondai-y rainbow where the secondary is 

 seen high above the primary and with the sequence of 

 tho coloui-s reversed, but there were two rainbows 

 immediately one within the other, both equally bright 

 and broad and the colours in each following the same 

 order as in that of a primaiy bow — the red of the inner 

 bow and the violet of the outer being apparently in 

 contact as closely as the other bands of colour usually 

 are seen. It occurred to me that there might possibly 

 have been two showers falling at the same time with a 

 dry interval between, and that I had seen a rainbow 

 upon each at such an angle as to exhibit one in apparent 

 contact with the other, but of this I cannot be sure. 

 The rain as it passed over me was a continuous shower, 

 and the length of the clear open portion of the valley 

 down which the storm drifted was not much more than 

 a mile. R. T. Lewis. 



Ealing, W^., 



1901, August 2. 



[The double rainbow, to which reference is made in 

 the above letter, was probably an ordinary primary bow 

 with a bright supernumerary bow adjacent to it on the 

 interior edge. The appearance cannot be explained in 

 the manner suggested by Mr. Lewis, nor by any simple 

 geometiical theory. Supernumerary bows, of which 

 several are sometimes seen on the inner edge of the 

 primary bow, and occasionally on the outer edge of the 

 secondary bow, are due to the interference of light, and 

 the angular distances between them and the principal 

 bow depend upon the diameters of the raindrops. A 

 full investigation of the phenomena will be found in 

 Preston's "Theory of Light," Ai't. 301. Some interest- 

 ing correspondence on the subject appeared in 

 Knowledge for December, 1900, and Februai-y, 1901. 

 — Ed.s.] 



BKlTfSfi 





h 



ORNiTHOLOCrCAD^^' 





Condueted by Harry F. Witherby, f.z.s., m.b o.u. 



Blve-Tits Nestim; i.x a Pu.mf.-A pair of Blue-Tits 

 have for several years built about 15 inches down the 

 inside of a pump here. Each time the handle is raised 

 — and the pump is in constant use — the machinery 

 works up through the nest without in the least dis- 

 turbing the birds. The parent birds enter the pump 

 by an aperture above the handle and leave it by one 

 below. — William Charles Tetley, Aspley Guise, Beds. 



Red-throated Pipit (AntJius cervinus) in Ireland 

 {Zoologist, July, 1901, pp. 264-267).— Mr. F. Coburn 

 records that he obtained in Co. Mayo on May 26, 1895, 



