September 1, 1894.] 



KNOWLEDGE 



207 



On tlie Continent, the auroral blank was much less 

 complete than m this country. Gassendi's aurora of 

 September 12th, 1621, was seen as far south as Aleppo; 

 Cromerus registered the passage of " whole armies " 

 across the sky in 1629 ; in 1640, south polar lights were 

 visible in Chili every night of February and March, and 

 some corresponding appearances were noted in northern 

 latitudes. By the middle of the century, however, polar 

 lights had virtually died out everywhere, except perhaps in 

 northern Scotland, where the " merry dancers " were seen 

 without surprise in 1691. But even in Iceland and 

 Norway they became so rare as to be considered portentous, 

 and their reappearance at Copenhagen in 1709 was 

 greeted with consternation and amazement. De Mairan, 

 in his " Traite de I'Aurore Boreale," makes the curious 

 remark that a great extension of the zodiacal light attended 

 the auroral outburst of 1716. 



As regards the solar corona during the " prolonged 

 minimum," it appears probable that (as Mr. Maunder 

 suggests) its radiated structure was in abeyance, but there 

 is positive proof that the inner corona maintained at least 

 its average brightness in 1666. The partial solar eclipse 

 of June 22nd in that year, being viewed through Boyle's 

 sixty - foot telescope by Hooke, Pope (Professor of 

 Astronomy in Gresham College), and others, " there was 

 perceived a little of the limb of the moon without the disc 

 of the sun, which seemed to some of the observers to come 

 from some shining atmosphere about the body either of 

 the sun or moon."* 



Yours faithfully, 



Agnes M. Clerke. 



.THE PROGRESS OF ASTRONOMICAL PHOTOGRAPHY, by 

 H. C. Russell, F.R.S., Government Astronomer, Sydney. 



To the Editor of Knowledge. 



Dear Sir, — Mr. Eussell chose wisely the subject of his 

 recent presidential address before the Mathematical Section 

 of the Australasian Association for the Advancement of 

 Science. With what authority he is entitled to speak 

 upon it, your readers can judge for themselves from the 

 specimens of his photographs reproduced in Knowledge. 

 The delineations obtained by him of the Magellanic clouds 

 and of the Coal-sack region of the Milky Way have, indeed, 

 a significance which is as yet very far from being ex- 

 hausted. The story that he now recounts is a marvellous 

 one. " The results," be truly says, " obtained by means 

 of photography come upon us so fast that one hardly 

 realizes their importance." The method has developed in 

 so many different directions, and lent itself so readily to 

 specialization, that their history, short though it be in 

 time, has already assumed an exceedingly complex 

 character. Mr. Russell has adopted a strictly chrono- 

 logical mode of treating it, and has brought together in 

 small compass a large amount of valuable information ; 

 but with some startling omissions. Thus, Prof. Barnard's 

 name is not so much as mentioned. Yet the fame of his 

 achievements in this department is world-wide. We need 

 only recall his initiation of galactic photography in 1889, 

 and his subsequent successful prosecution of it ; his 

 registration, from night to night, of changes in comets' 

 tails, his discovery on a sensitive plate, in 1892, of an 

 additional member of Jupiter's cometary family, besides 

 his exquisite picture of the solar corona of January 1st, 

 1889. Dr. Max Wolf and M. von Gothard, each of whom 

 has done important and distinctive work in celestial photo- 

 graphy, incur similar oblivion ; but they may take heart 



• Philosophical Tramactioas, Vol. I., p. 295. 



when they find Dr. Gill no better treated. It seems 

 incredible that a man who is the very head and front of 

 photographic star-charting should be passed over in such 

 a record as Mr. Russell's ; but such is the fact. Not 

 only was the star-crowded background of his portrait of 

 the " great September comet " of 1882 the object lesson 

 from which astronomers learned its possibility, but he was 

 foremost in starting and developing in detail the inter- 

 national scheme now in course of execution at a score of 

 observatories. Above all, he set the example of doing, by 

 completing Argelander's Dairhnmstenmfi to the southern 

 pole. The resulting catalogue — the first photographic 

 work of its land — gives the places, accurate to within about 

 one second of arc, of some 350,000 stars. It is at present 

 rapidly passing through the press. Nor should it be 

 forgotten that Prof. Kapteyn generously devoted five years 

 to the labour of its preparation from the Cape plates. 



We look in vain, too, in this address, for any allusion to 

 Nova AurigsB, the first "blaze-star" investigated photo- 

 graphically, or Nova Norma?, the first similar object dis- 

 covered photographically. Indeed, none of Mrs. Fleming's 

 valuable detections are chronicled. Nor do we find the 

 slightest reference to the self-registration of new asteroids 

 or of meteors, although researches of the latter kind seem 

 about to enter upon a fresh stadium of progress through the 

 possibility, just demonstrated by Dr. Elkin, of determining 

 the radiants of meteoric showers from the imprinted 

 trails of their constituents.! Mr. Russell, however, 

 eagerly anticipates novelties, and is full of well-grounded 

 confidence in the future. He himself promises a photo- 

 graphic transit recorder, and indicates several lines of 

 imminent advance. Obstacles there are, but only to be 

 overcome. " The army of science," he continues, " is in 

 one respect like the army of war — it is stirred to con- 

 quering effort by the difficulties that stand in the way. 

 Given a citadel to be won, and there is always a forlorn 

 hope to win it." These words breathe the true spirit of a 

 scientific pioneer. 



Yours faithfully, 



A. M. Clekke. 



To tlie Editor of Knowledge. 



Dear Sir, — The Rev. A. S. Wilson, in an article on 

 " Types of Floral Structure" which appears in the July 

 issue of Knowledge, says " there is no apparent reason 

 why the carpels and stamens should not occasionally 

 change places, and an explanation of this invariable order 

 is still a desideratum." 



A sufficiently obvious reason, it seems to me, is found 

 in the fact that the stamens of the flower are not persis- 

 tent. As soon as their pollen is shed, their work is done, 

 they become useless and decay, or fall oft'. If they occupied 

 the centre of the flower they would be prevented from so 

 doing by the carpels, which persist long after the stamens 

 have decayed, and in the case of syncarpous pistils there 

 would be a central cavity in the fruit enclosing the dead 

 stamens. 



Besides this, if the stamens were central it would be 

 easy for their pollen to become dusted on to the adjacent 

 stigmas, an arrangement which Nature has, in the great 

 majority of cases, endeavoured to avoid. 

 Yours faithfully, 

 Kingswood School, Geo. H. Pethybbldge, B.Sc. 



Bath, 

 August 14th, 1894. 



t Dr. Elkin's success ia too recent to hare been known to Mr. 

 Russell when his ttddress was delirered. 



