288 



NA TURE 



[Feb. 12, 1874 



in 1777, and continuing his observations till 1783. He 

 first noticed the eccentric position of the two white spots 

 in the polar regions, as well as their diminution from 

 solar action ; 5 out of his 31 figures show a broad white 

 band passing obliquely across tue disc, and he speaks of 

 changes in the markings from passing clouds and va- 

 pours : some of his dark spots can be identified with more 

 recent representations, but not the whole. Of the nume- 

 rous drawings (217) of Schroier, Kaiser was unable to 

 avail himself, as the Areographische Fragmente, rescued 

 from the disastrous fire at LiUenthal in 1 813, were left 

 unpublished at his death. These, however, through the 

 intervention of Dr. Peters of Altona, have subsequently 

 been traced to their safe custody in the hands of Schroter's 

 descendants, and have recently been thorough y exammed 

 by Dr. Terby of Louvain, lOmse report has been published 

 by the Belgian Academic Royale des Sciences. From 

 the figures contamed in this, and another interesting es^ay 

 by the same astronomer, it appears that many coinci- 

 dences may be traced between the views of .Schroter and 

 other observers, though his preconceived idea of the 

 vaporous nature of the darker features deprived his ob- 

 servations of some of the value otherwise due to them as 

 the results of eminent zeal and perseverance. 



Passing by several observers of minor note, of whom 

 Kaiser has given a minute enumeration, we reach the oppo- 

 sition of 1830, which the near concurrence of the aphelion 

 of the Earth and the perihelion of Mars rendered 

 eminently favourable, enlarging the apparent diameter of 

 the latter to 23'"l. The close and systematic investiga- 

 tion then entered upon by Beer and Madler forms a most 

 important epoch in the progress of areography, and for 

 the first time a series of drawings were executed, little 

 resembling anything previously known, which have ever 

 since been referred to with confidence as a starting point 

 for future inquiries, and which, it might have been hoped, 

 would have set many questions at rest : and so they did ; 

 but as Kaiser remarks, Liter representations have again 

 unsettled points which had been supposed to have been 

 then decided. The comparative failure of the same ob- 

 servers in subsequent oppositions admitted of explanation 

 from the increased distance and altered presentations 

 of the planet ; and little advance was made by Mauler in 

 1841, even with the renowned refractor at Dorpat, to the 

 care of which he had succeeded : the apparent diameter, 

 then, however, was only I5"l, its minimum, attained in 

 1837, being I3"'3. Of the near approach in 1S45, when 

 the disc was enlarged to 23"-5, no observations seem to 

 have fallen into Kaisers hands, excepting those of the 

 American astronomer Mitchtll. Confining ourselves still 

 to the more important representations, at the expense of 

 doing scanty justice to the Professor's elaborate memoirs, 

 we find that 1854 produced the beautiful designs of Jacob, 

 and 1856 the still more delicate ones of Do La Rue, both 

 great advances on anything previously published. In 

 1858, Secchi, who had been for some years at work at 

 Rome, brought out a series of drawings in much harmony 

 with themselves, but only partial agreement vyith previous 

 delineations. At length came the favourable opposition 

 of 1 862, when the point was taken up by many of the first 

 observers armed with some of the most powerful telescopes 

 in existence ; but the result, we regret to add, was very 

 different from what might have been anticipated. Secchi, 

 with his magnificent achromatic, Lassell and Rosse with 

 their colossal relkctors, pro iuccd such an unsatisfactory 

 and in part contradictory set of drawings as had never 

 been published before, fhe weather was not always in 

 fault ; and though Mars was rather low, Lassell repeatedly 

 found very sharp definition ; Lord Rosses excellent 

 draughtsman once used a power of 1,200 ; and the quality 

 of Secchi's instrument and sky compensaied to a great 

 extent for his smaller aperture ; but then the expected 

 clearing up of difficulties terminated in the annoyance of 

 disappointment. Kaiser assures us that nowhere are 



there such discrepancies as between Rosse and Lassell, 

 even when the same hemisphere was obviously in sight ; 

 it could hariily be imagined that they had the same spot 

 in view : and Secchi is so far from setting the matter 

 straight, that his figures scarcely seem to refer to the same 

 body ; and for any purpose of accurate deduction the 

 Leiden Professor felt obliged to put all three aside. He 

 is even induced to say, " the largest telescopes give the 

 worst results, and show themselves very liable to mislead 

 the observer : correct delineations of the celestial bodies 

 require before all things a very practical designer that 

 gives way to no fancies ; and such a designer is not apt 

 to possess the most powerful telescopes of the earth." 

 We are here merely reproducing the censor's words, with- 

 out venturing an opinion as to the soundness of his 

 criticism. 



But, f irtunately as it would seem for areogrophy, instru- 

 ments of more moderate dimensions were employed to 

 better purpose during that and the subsequent opposition 

 of 1864 ; and the agreement of the beautiful designs of 

 Lockyer in the former year with those taken by Kaiser 

 himself, then and in 1864, as well as wiih those of 

 Schmidt and Phillips, was far more satisfactory : and 

 the same might be said to a considerable extent as to 

 Dawes, whose instrument, however, was of a superior 

 rank.* The difference between Lo:kyer and Lassell, in 

 one instance, was so wide, that identity of date alone 

 proves that they had the same hemisphere under their 

 eyes ; while, on the contrary, the concurrence between 

 Lockyer and Kaiser, though the latter speaks with great 

 diffidence of his own designs, justified him in believing 

 that a pretty correct representalion had been attained of 

 a broad girdle round the equator. 



The labour which the Leiden professor has bestowed 

 upon a comparison of all the least discordant drawings, 

 and the punctilious accuracy of his protracted discussions, 

 would be little appreciated from so brief a sketch of them 

 as can be attempted here. He was himself so little pleased 

 with the result as to express an opinion that the only safe 

 inference from the oppositions of 1S62 and 1864 is, that 

 the art of drawing celestial objects is at much too low a 

 pitch to justify accurate deductions as to their physical 

 character. And this, though it looks like the language of 

 disappointment, and is hardly reconcileable with the 

 striking agreement which he often remarks between the 

 drawings of difterent observers, or the same observer 

 at different times, seems to have been his deliberate 

 impression. He ascribes the variations in part to the 

 differences of presentation and pe'rspective, in part to 

 faulty delineation ; and while he admits that atmospheric 

 condensations may have occasioned small t^pparent 

 changes, he thinks on the whole that they are evidences 

 of the unsteadiness of our air, leaving almost always an 

 uncertainty as to ihe minuter spots and shadings, and a 

 want of confidence in the correctness ol one's own deli- 

 neation. The discrepancies among his 412 designs are 

 so " enormous " that no one would believe that they were 

 intended for the same body. These diff'eiences arose, 

 however, in part from natural causes. Even in the most 

 favourable case, the spots are only seen with any distinct- 

 ness or in their true form in the centre of the disc ; those 

 lying near the limb being greatly foreshortened and not 

 recognisable in their real shape ; and this difliculty is 

 Very considerably enhanced by the imperfect transparency 

 of the planet's atmosphere and its frequently strongly 

 illuminated precipitations. The inclination of the axis 

 may vary its position at difterent times about 60^ as re- 

 gards the spectator, and consequently different oppositions 

 bring before him entirely different features in that central 

 position where alone they can be well observed or drawn. 



* It is much to be regretted that only .1 part of the drawings of this great 

 observer have as yet been published in Jac-sintite. Those given in tllc 

 Monthly Nolices (XXV., 225) omit, as Kaiser remarks, some of the most 

 curious presentations of the globe ; and the reproduction of others by 

 Proctor does not profess minute accuracy. 



