588 



NA TURE 



OCTOBKK II, 190b 



At the opposition of 1894 ^" i8-incli glass made 

 bv Brasliear was employed, but for tfie oppositions of 

 i8qb and later the 24-inch objective mentioned above 

 was made and mounted for the observatory by Alvan 

 Clark and Sons, " the last glass, as it chanced, of 

 that famous firm."" 



Even at Flagstaff Mr. Lowell was not content with 

 the astronomical conditions of .seeing all the year 

 round. For this reason, at the opposition of 1896-7, 

 he determined to try the conditions in Mexico for the 

 winter months; observations were therefore termin- 

 ated in November, iSg6, and not resumed until 

 December 30. In the meantime the dome and tele- 

 scope were transported and set up at Tacubaya, near 

 the city of Mexico, in latitude iq° 26' N. This 

 temporarv change resulted in .a long series of post- 

 opposition observations. 



\\'ith regard to the method of recording the observ- 



- Longitude 270" at the opposili 



(Lo 



ations, drawings, notes, and micrometer measures 

 formed the usual routine. The drawings were made 

 on circles about 40 mm. in diameter, a convenient size 

 for combining " most satisfactorily sufficient space 

 with possibility of keeping proportions." As a rule, 

 we are told, the drawings were of the complete 

 disc, and were made as nearly instantaneously as 

 possible. 



Coming now to the observations themselves, and 

 the numerous clear drawings which accompany them, 

 it seems extremely difficult to refer to any particular 

 set of them, as they are all so full of interest. The 

 observations bring out, however, very clearly the 

 apparent discrepancies which have arisen between 

 observations taken of the same region, but at different 

 times, by well-known Martian observers. Thus, to 

 take a case in point, in the opposition of 1894 Mr. 

 Lowell relates how, in observing the region about 



NO. 1928, VOL. 74] 



Syrtis Major, which was central on the disc, the most 

 prominent features were tongues of shade which lay 

 between Hellas and Naochis, and nearly joined the 

 .Syrtis to the blue band bordering the cap. " For the 

 rest no detail could be made out upon the disc, except 

 for two dark spots where the coast-line dipped to 

 enter the Great and Little Syrtes respectively ; the Only 

 salient points these of an otherwise featureless face. 

 Not only was there no sign of a canal, but even the 

 main markings showed dishearteningly indefinite." 



.Such an apparent lack of markings was, as Mr. 

 Lowell points out, a matter of the Martian date. It 

 was, as he says, " the very nick of time to see nothing. 

 For the part of the planet most presented to the 

 earth was then at the height of its dead season." 

 Mr. Lowell states, further, " when we consider that 

 such is always the face the planet shows when at its 

 nearest to the earth, and that till lately such time 

 was commonly chosen for examining 

 its disc, it is small wonder that 

 previous to Schiaparelli the strange 

 canal-system should have escaped de- 

 tection." 



The above extracts will, we think, 

 convey to the reader the pitfalls into 

 which the Martian observer can 

 stumble in consequence of the seasonal 

 changes on the planet. 



.\gain, Mr. Lowell gives instances 

 of markings which undergo a secular 

 v;iriation covering many years. Thus 

 a conspicuous single canal, called by 

 Lowell Sitacus, connecting the eastern 

 fork of the Sabaeus Sinus with the 

 north-east corner of Aeria, wa.s not 

 seen by Schiaparelli. It was such a 

 salient feature in 1894 that he could 

 not have missed it had it been there. 

 Cerulli noticed it in 1896, and it has 

 been seen at all subsequent oppositions 

 as a fairly conspicuous canal. This 

 canal exemplifies, as Mr. Lowell says, 

 " the truth of a • deduction of Schia- 

 parelli that the canals were curiously 

 subject to secular wa.x and wane." 



.Another canal, LHysses, unrecorded 

 bv Schiaparelli, which in 1894 was 

 comparable in strength with the Gigas 

 or the Titan, is a further inst.ance of 

 secular change. 



It is interesting to note that Mr. 

 Lowell gracefully explains the great 

 difference between the number, 183, of 

 canals seen at Flagstaff at the opposi- 

 tion of 1894 and that recorded by 

 Schiaparelli, 79, as " due solely in 

 consequence of better observational conditions of one 

 sort and another."" 



Among other results of this opposition was the 

 clear detection of the seasonal change; an increase in 

 the number of the oases which lie at the intersection 

 of the canals; an extension of the canals in the dark 

 regions which conclusively showed that the dark areas 

 were not "seas"; observations on the changes of 

 shades of the dark areas showing that they were not 

 bodies of water; and, finally, peculiar m.-u'kings, 

 termed " nicks,"' were observed where the canals 

 entered the light regions. 



Space does not permit one to enter into anything 

 like detail with reference to the observations made 

 at the succeeding oppositions. Iii that of 1896 there 

 was sufficient evidence to show that, as Schiaparelli 

 had pointed out, the doutjling of the c;mals was not 

 wholh a seasonal effect. .\nother observation of 



ntre of the di; 



