June 8, 1909J 



NATURE 



Ruwenzori "). M. Fo^ made considerable collections 

 of fish in Central Africa, of mollusca, insects, spiders, 

 licks, and crustaceans. He also brought back 

 Medusw from Tanganyika. These Medusae serve as 

 a text for a very interesting article by M. Charles 

 Gravier on the Medusae of the Victoria Nyanza, of 

 Tanganyika, and of the Niger basin. Perhaps the 

 most important contribution to this rccueil is the 

 treatise by M. Louis Germain on the molluscs of 

 Tanganyika, notably those collected by M. Foi. M. 

 Fo^'s own remarks on the tsetse fly are worthy of 

 attention. H. H. Johnston. 



THE PLANET MARS, 1890-1901. 



La PlanHe Mars et ses Conditions d'Habitabilitd. By 

 Camille Flammarion. Tome ii., Observations faites 

 de 1890 h 1901. Pp. 604. (Paris : Gauthier Villars, 

 1909.) Price 12 francs. 



IN the year )893 we had the great pleasure of giving 

 our readers some account (vol. xlvii., p. 553) of 

 the very excellent and complete summary of the 

 observations of the planet Mars, made between the 

 epochs 1636-1890, compiled by the distinguished 

 French astronomer, Monsieur Camille Flammarion. 

 This work, containing no fewer than 604 pages, pre- 

 sented us with a most interesting survey of the 

 progress made in enumerating and deciphering the 

 markings observed on the planet's surface. It com- 

 menced with the earliest known observation of the 

 planet, namely, that of the Neapolitan astronomer 

 Fontana, on August 24, 1638, who wrote : — 



" 1636. Martis figura perfecte spherica distincte 

 atque clare conspiciebatur. Item in medio atrum 

 habebat conum instar nigerrimae pilulse. 



" Martis circulus discolor, sed in concava parte 

 Ignitus deprehendebatur. 



" Sole excepto, reliquis aliis planetis, semper Mars 

 candentior demonstratur." 



The volume concluded with the observations made 

 in the year 1890, including the first photographs of 

 the disc of Mars made by Prof. W. H. Pickering at 

 Mount Wilson, California, on April 9. 



In Martian cartography the year 1890 seems to-day 

 a very long time ago. The pioneers did their work 

 well, and the great tradition which fell on the 

 shoulders of those who were busy with Mars up to 

 1.590 was well maintained, and a great amount of new 

 knowledge secured. Since that year the attack on the 

 planet, to unravel the secrets of its visible features, has 

 been no less severe, and to-day the knowledge gained 

 is only a new incentive to further research. 



If we were to be asked to state three or four of the 

 more recent and most important discoveries in relation 

 to the planet Mars, we should be inclined to say as 

 follows : — 



(i) That the dark areas on the planet which were 

 considered to be seas have been shown to be traversed 

 by permanent lines, and that, therefore, the water 

 surface explanation had to be abandoned (Pickering 

 and Douglas, 1892). 



(2) The successive development of the canals accord- 

 ing to the Martian seasons (Lowell). 

 NO. 2071, VOL. 81] 



(3) The photography of the canals themselves 

 (Lampland, 1903-5). 



(4) The photography of the spectrum of water 

 vapour in the Martian atmosphere (Slipher, 1908). 



While the above may be considered as four of the 

 important results secured since iSgo, there is a host 

 of many other valuable advances which w'ill be found 

 recorded in the volume under review. 



Monsieur Flammarion has done his work exceed- 

 ingly well, and, with masterly instinct, describes, fits 

 together, and discusses the observations, made be- 

 tween the years 1890 and 1901 by a very great number 

 of workers, in a logical and interesting manner. 



Before commencing to give in detail the observa- 

 tions of the first epoch, 1892, he rightly refers at some 

 length to the fine memoir published in 1896 by the 

 celebrated Italian astronomer, M. Schiaparelli, the 

 discoverer of the canals. This memoir is devoted to 

 a discussion of his observations of the Opposition 

 1883-4, while a sixth memoir, published in 1S99 and 

 here referred to, contains his observations made at the 

 Opposition of 1888. 



Space does not allow us, nor indeed is it necessary, 

 to enter into any detail into the successive series of 

 observations which are here marshalled together. 

 The reader must be left to peruse the volume himself 

 and form his own conclusions, but even he will be 

 astonished at the wealth of matter which is brought 

 together under one cover. 



As in the previous work, there is a great number 

 of illustrations accompanying the text, and these add 

 materially to the understanding of the changes of 

 Martian features. 



. At the end of the volume, M. Flammarion, with the 

 help of M. Antoniadi, has constructed a key-map of 

 the surface features of the planet, which gives us 

 an idea of the complicated system of markings which 

 is the result of the observations up to the year 1901. 



As has been mentioned above, some important 

 additions to our knowledge of Mars have resulted 

 from observations of more recent date, and we can 

 only suppose that M. Flammarion has in hand vol. iii., 

 which will, we hope, in due course be published, and 

 be as valuable a contribution to astronomical science 

 as its two predecessors. 



In conclusion, we may quote M. Flammarion 's 

 remarks with regard to the habitability of Mars, since 

 the subject has recently been prominently brought 

 forward : — 



" Mais il me semble que, dans toutes ces inter- 

 pretations, je suis moi-meme un peu terrestre. II y a. 

 sans doute 1^ d'autres Elements, non terrestres, mais 

 martiens, ou, tout au moins, des conditions toutes 

 differentes de celles de notre habitation. Que cette 

 planete soit actuellement le siege de la vie, c'est ce 

 dont ti§moignent toutes les observations. Mais il nous 

 est encore impossible de nous former aucune id^e 

 judicieuse sur les formes que cette vie a pu revgtir, 

 formes assurement differentes de n6tres. L'n mystfere 

 impi^n(5trable enveloppe encore aujourd'hui ce passion- 

 nant problfeme, qui est, en definitive, quoi qu'on en 

 passe, le but, peut-etre inaccessible, de toutes les 

 recherches de I'Astronomie planetaire. Mais ne d^ses- 

 p(§rons jamais! Qui salt ce qui sommeille dans 

 I'inconnu de I'avenir? " 



William J. S. Lockyer. 



