NATURE 



553 



THURSDAY, APRIL 13, 1893. 



THE PLANET MARS. 

 La Planite Mars et ses Conditions (V HabitabilittK Par 

 Camille Flammarion. (Gauthier-Villars et Fils, 1892.) 



IN this very handsgrne volume the author brings 

 together every available observation and piece of 

 information that can be gathered from published and 

 unpublished works with respect to our sometimes very 

 near neighbour, the planet Mars. To make such a com- 

 pilation as this, is, as every one will acknowledge, no light 

 task ; and since up to the present no one has made any 

 attempt to collect existing observations and discuss 

 them (although perhaps the value of this book is the 

 more enhanced thereby) the difficulty of the undertaking 

 has been very considerable, but in such hands as M. 

 Flammarion's it has been thoroughly mastered. 



With regard, first, to the form of arrangement which 

 the author has thought advisable to adopt — since in a 

 work of this kind many courses are open depending on the 

 standpoint from which the book is written — the writer 

 might, in the first instance, have divided the text into 

 chapters dealing with the climate, calendar, heat, mass, 

 density, geography, &c., treating each of these at full 

 length, and discussing all the observations bearing on 

 each separately. That this would have formed a good 

 and logical sequence is unquestionable, but it is accom- 

 panied by many drawbacks, the chief of them being 

 that as observations increased and our knowledge con- 

 sequently advanced, each part of the work would have to 

 be rewritten, or, at any rate, undergo a thorough revision. 

 The method actually chosen is one which will seem 

 more simple and therefore appeal more to the astronomer, 

 and will perhaps be productive of better discussion. M. 

 Flammarion places the facts before the reader in simple, 

 chronological order, tracing out the work on the planet 

 from the very first observations, step by step, down to 

 those made during the opposition of 1892. 



The volume is divided into two main parts, the first 

 including the exposition and discussion of the obser- 

 vations themselves, and the latter containing the con- 

 clusions that have been drawn from the study of all the 

 facts. The interval from 1636 to 1892— that is the whole 

 time covered by our records— is divided into three 

 chief periods, the first two of which terminate in the 

 years 1830 and 1877 respectively. 



Dealing first with the period commencing with the 

 observations of Fontana (1636-1638), we are at one of 

 the most interesting parts of the book. Here the author 

 has been plunging into all the old original records, and 

 has treated us to the tit-bits both as regards illustrations 

 and text. As we cannot here conveniently produce the 

 earlier drawings of the planet as made by Fontana, but 

 which are represented in this volume, we may at least give 

 the original observations as recorded in words : — 



" 1636. Martis figura perfecte spherica distincte 

 atque clare conspiciebatur. Item in medio atrum 

 habebat conum instar nigerrimic pilulx. 



" Martis circulus discolor, sed in concava parte ignitus 

 deprehendebatur. Sole excepto, reliquis aliis planetis, 

 semper Mars candentior demonstratur." 



NO. 1224, VOL. 47] 



The second drawing, which was made on August 24, 

 two years later, was accompanied with the text : — 



"Martis pilula, vel niger conus, intuebatur distincte 

 ad circuli, ipsum ambientis, deliquium, proportionaliter 

 deficere : quod fortarse Martis gyrationem circa pro- 

 prium centrum significat." 



Following Fontana ; Riccioli, Hirzgarter, Schyrle de 

 Rheita, Hevdlius, and Huygens (1656) were the next 

 to make a special study of this planet, the last 

 mentioned of whom added much to the know- 

 ledge of the planet's surface markings. Up to the 

 end of this period (1830) the number of observers, and 

 consequently the number of observations had very much 

 increased, while the rapid stride made in the perfection 

 of the telescope was not the least important factor in this 

 advance. Summing up the conclusions which can be 

 drawn from these 192 years of observations it may be said 

 that they related more to the elements of the planet 

 than to its surface features, although spots varying in 

 size had been many times noticed ; the general idea of 

 the different shadings as representing land and water had 

 been thrown out, and the polar caps had been recorded as 

 variable and not coincident with the geographical poles. 

 The second period, commencing in the year 1830, opens 

 with an account of the fine series of observations made 

 by Beer and Madler. It was about this time that the 

 real geography of the planet's surface began to be better 

 known, and a systematic method of mapping brought 

 into vogue. Following these two workers come a host of 

 others, all adding their mite, in some cases rather a large 

 one, to solve the riddle relating to this orb. Among 

 these we may mention ; Warren de la Rue, Secchi, several 

 of whose fine drawings are here inserted ; Lockyer, 

 whose drawings, sixteen of which appear here, and " sont 

 les plus important pour la connaissance de Mars de tous 

 ceux que nous ayons otudies depuis les premieres pages 

 de cet ouvrage " ; Phillips, Lord Rosse, Lassell, Kaiser, 

 Flammarion, Trouvelot, &c. With such observers as 

 these, and many others as able, but whose names are too 

 numerous to mention, it is no wonder that good work was 

 done, and our knowledge by the year 1877 greatly 

 extended. More accurate values for the elements were 

 deduced, land and water features confirmed, cloud drifts 

 observed, variations in the polar caps again noticed, &c., 

 in fact, to put it shortly, all observations pointed to 

 a singular likeness of Mars, physically speaking, to the 

 earth herself. 



In the third and last period-^the Martian cycle from 

 1877 to 1892 — we have observations extending over as 

 many as 239 pages of the volume. The epoch com- 

 mences very appropriately with Prof. Asaph Hall's 

 discovery of the two small satellites, and introduces to us 

 the observations of Schiaparelli, whose work on this 

 planet has been rewarded by such brilliant discoveries. 

 To enter, however briefly, into the mine of interesting 

 arid valuable material here brought together would lead 

 us far beyond the limits of this article, but we must leave 

 it to the readers of this journal to refer to the book itself; 

 suffice it to say that ISL Flammarion has given each 

 observer his just due and merit. 



Arriving now at the second part, which gives the results 

 deduced from the general study of the planet, M. Flam- 

 marion is also quite at home, and in his masterly way 



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