February 28, 1901] 



NA TURE 



42 1 



apparatus ; but on closer examination about half a dozen 

 delicate dark (Fraunhofer) lines were made out by Dr. 

 Halm, extending from a little below D to about F. 

 The spectrum of the Nova, at its present stage, is there- 

 fore of a distinct but feebly developed solar type. The 

 existence of these lines I was able to confirm, but the sky 

 became gradually obscured before their positions could 

 be satisfactorily determined. 



At about the same hour a photograph of the Nova was 

 secured by Mr. Heath at a time when all the neighbour- 

 ing stars were obscured by haze. Except a very short 

 interval on the 23rd, the sky here has been completely 

 overcast since the 22nd. 



The Nova was independently discovered by Mr. J. E. 

 Gore at Dublin at iih. 15m. Dublin time on the 22nd, 

 and by Mr. W. B. Dodd and Mr. H. Wake, of White* 

 haven, on the 23rd inst. Ralph Copeland. 



Royal Observatory, Edinburgh, February 25. 



On the night of the 25th observations were made at 

 the Solar Physics Observatory, South Kensington, the 

 general results of which have been stated by Sir N. 

 Lockyer as follows in a letter to the Times : — 



(i) The spectrum strongly recalls that of Nova 

 Aurigae. 



(2) There are at least two light sources involved ; one 

 with a dark-line spectrum, the other giving chiefly the 

 bright lines of hydrogen, helium, asterium and calcium. 



(3) Some of the bright lines are probably reversed. 



(4) The broadening of the bright lines is considerably 

 greater than that observed in Nova Aurigte. 



(5) It has been determined by a comparison spectrum 

 of Bellatrix, on the same plate, that the middle of the 

 bright lines occupies nearly the normal position in the 

 spectrum ; the greatest breadth of lines observed extends 

 over some 30 tenth-metres. 



(6) The centres of the bright and dark lines are 

 separated by about 15 tenth-metres, showing a differential 

 velocity of somewhere about 700 miles per second between 

 the colliding light sources. 



(7) The star is keeping up its magnitude so far as may 

 be gathered from a very brief observation made between 

 clouds on Friday. To-night (February 25) it has been 

 brighter than Aldebaran, slightly less bright than Capella. 



PHOSPHORESCENCE AS A SOURCE OF 

 ILLUMINATION IN PHOTOGRAPHY. 



T N certain libraries there exists a fixed rule that no 

 *- books may be removed. This being so, all extracts 

 and copies of plates and engravings have to be made in 

 the libraries. Reproduction by the methods of ordinary 

 photography is most inconvenient, since the employment 

 of artificial light is strictly prohibited ; also the intro- 

 duction of a camera, and its manipulation in a library, 

 are surrounded by many difficulties. These circumstances 

 led me to devise the following method for obtaining copies 

 of plates, engravings, printing and writing. A piece of 

 cardboard is coated with a phosphorescent substance, and, 

 after sufficient exposure to the light of the sun or of an arc 

 lamp, it is placed at the back of the engraving or writing 

 to be copied ; on the face of the engraving or writing a 

 dry photographic plate is placed, and then the book is 

 closed for a certain time, depending on the nature and 

 thickness of the paper used in the book. I find that the 

 period of time lies between eighteen and sixty minutes. 

 The plate is then withdrawn and stored in a dark box 

 for development. The dry plate is easily manipulated 

 under a cloth, which shuts ofT all light and covers the 

 book during the operation. The results are sufficiently 

 good for most purposes — in the case of some papers the 

 fibrous structure is shown ; this very slightly detracts 

 from the clearness of the copies made by this process. 

 Neither the luminous substance nor the dry plate injure 



NO. 1635, VOL. 63] 



the book in any way, so that the method' may be employed 

 in the case of valuable prints and engravings (Fig. i). If 

 films be used instead of plates, a large number of copies of 

 different engravings in the same book may be made at 

 the same time. The time of exposure to the phosphor- 

 escent backing is shortened considerably by placing the 

 phosphorescent card on a warm surface, such as that of 

 a metal vessel heated to about 20^ C. with hot waters 



when films are employed, this temperature should not 

 be exceeded. In an experiment made in the laboratory 

 I found that the phosphorescent substance under normal 

 barometric pressure became brightly luminous when sub- 

 jected to the brush discharge of a Tesla inductor ; the 

 discharge from an ordinary induction coil fails to produce 

 the same effects. F. Jervis-Smith. 



THE ROYAL SOCIETY'S ADDRESS TO 

 THE KING. 



ON Saturday last His Majesty the King received 

 deputations with addresses from the Universities 

 of Oxford and Cambridge, General Assembly of the 

 Church of Scotland, the Corporation of the City of 

 Liverpool, and the Royal Society. 



The Royal Society was represented by Sir WiUiam 

 Huggins, K.C.B. (president), Mr. A. B. Kempe, 

 treasurer (mover). Sir Michael Foster, M.P., secretary 

 (seconder), Dr. T. E. Thorpe, C.B. (foreign secretary). 

 Lord Lister, Lord Kelvin and Sir J. D. Hooker (past 

 presidents), and Mr. W. H. M. Christie, C.B., Astro- 

 nomer Royal (vice-president). The following was their 

 address : — 



To THE King's Most Excellent Majesty. 



The Humble Address of the President, Council, and Fellows of 

 the Royal Society for Promoting Natural Knowledge. 

 Most Gracious Sovereign, — We, your Majesty's most dutiful 

 and loyal subjects the President. Council, and Fellows of the 

 Royal Society of London for Promoting Natural Knowledge, 

 humbly beg leave to offer our deepest and most heartfelt 

 sympathy with your Majesty in the great sorrow which has 

 befallen you in the death of your beloved mother, our late 

 Sovereign Lady the Queen. Your Majesty's loss is our loss, a 

 loss not only to ourselves, not only to all your Majesty's subjects 

 throughout the Empire, but to the whole world. During your 

 beloved mother's wise and beneficent reign under her thoughful 

 fostering care that natural knowledge which the society was 

 founded to promote has been promoted to an extent and in ways 

 never known before, and we feel sure that not in our time only, 

 but in the years to come, to the story of the advance of science 

 in the past century will be most closely linked the memory of 

 the goodness, the wisdom, the peerless worth of the august and 



