470 



NA TURE 



[September 13, 1S94 



contained a fine living Pjnthiilis, which was successfully trans- 

 ferred 10 a small tank provided with a supply of the fine mud 

 in which the animal lives. This worm has been kept under the 

 closest observation by Mr. Watson and his son during the whole 

 daytime and part of the night for the past week, and their care 

 and enthusiasm have been rewarded by the collection of a 

 number of drawings, photographs, and notes of the appear.ince 

 and movements of the .inimal. During that time the PanthaHs 

 has deserted its old tube, and has formed a new one in the mud, 

 fortunately using the glass of the tank for part of one side, so 

 that the processes of scooping out the mud and of putting on 

 the lining of mucous threads, and the various movements of the 

 animal, have been readily enough seen — if one does not mind 

 the incon%'enience of lying for hours in a cramped position on 

 the damp concrete floor of the aquarium room. The worm, 

 and Mr. Watson, are still alive and at work, and we may expect 

 a detailed account of their mutual labours from the latter when 

 his observations are completed. W. A. Herdm.\n. 



Por: Etin, .Vugust 31. 



15 he will have reached his most eastern point, and 

 from that time he will turn in his loop, and continue 

 his apparent journey in the westward direction, passing 

 into the neighbouring constellation of the Fish. 



The following table will perhaps be useful to those who 

 have not the data at hand. The times referred to are 

 Greenwich mean time. 



Symmetry of •' Aurelia aurita." 



Di'RiNG the last few months I have seen countless thousands 

 of living specimens of Aurdia aurita, and have paid special 

 attention to abnormal varieties. I have found not only such as 

 have throughout the five-fold symmetry, seen by Mr. Unthank 

 at Brightlingsea, as named in Nature for August 22, but have 

 with me on the Gliwfse .-specimens stained and mounted as lan- 

 tern slides having entire threefold and entire six-fold symmetry, 

 and one in which it is partially two-fold. I think it may be 

 said that in Suffolk and Essex, a few such abnormal varieties 

 occur per thousand of the normal. An imperfect four-fold 

 symmetry is much more common. H. C. SoRliV. 



Vacht Glimpse, Burnham, Essex, August 31. 



MARS AS HE NOIV APPEARS. 



CT.-\TISTICS are looked upon, as a rule, as hateful 

 ■^ things, but nevertheless it would be interesting to 

 know how many people out of the millions who walk this 

 globe will turn at this period a telescope, however small 

 It may be, in the direction of the planet Mars, which is 

 shining so brilliantly in our eastern heavens. Times 

 there were, no doubt, as for instance in the early 

 Babylonian and Egyptian civilisation, when Mars was 

 more generally the subject of scrutiny than to-day, 

 but then the appearance of this intermittent and 

 gradually brightening object made far different im- 

 pressions on the minds of those early observers. Karly 

 it was that the peculiar coloured rays cast by his shining 

 surface on this earth were lirst remarked. He was known 

 to the Greeks and Hebrews as the fiery planet, and 

 in Sanskrit he was referred to as like " burning coal." 



To-day, however, the case is quite different. Many 

 there are who may happen to notice an object more 

 brilliant than usual in the heavens, and make some brief 

 allusion to the fact, and trouble himself or herself no 

 more about it, but it is to the increasing few that his 

 appearance is of the greatest interest. To those who have 

 once made use of even a small telescope to observe the 

 planets, the fact that the nearest, and, it may be added, 

 the most interesting, of iliem, namely Mar,-, is a|)proach- 

 ing us day by day, will be certam to raise a strong 

 desire to catch another glimpse of his disc under such 

 favourable conditions. 



So much has been written about the markings of his 

 surface, which represent huge areas of water and land, 

 to say nothing of the most curious network of canals, 

 that reference only to the very recent work on them will 

 here be dealt with. 



A few brief remarks, before proceeding, as to the 

 position of the planet in the heavens, and to the approach- 

 ing opposition. 



Firstly, as to position. At the present time Mars is 

 movmg easterly in the heavens, situated at the southern- 

 most corner of the constellation of Aries. By September 



NO. I29S, VOL. 50] 



The fact of Mars being the first superior planet reckon- 

 ing from the sun, his opposition, or in other words, the 

 position in which he is to be found in his orbit when on 

 the same side of the sun as the earth, with all three 

 bodies in a straight line, afibrds us a good opportunity 

 for studying his surface features. Owing, however, to 

 the non-concentricity of planetary orbits, his distance 

 from the earth at these times is always varying, and this 

 explains why some oppositions are more favourable for 

 observation than others. The nearest approach of Mars 

 to the earth may be approximately given as 35,000,000 

 miles, his distance at the coming opposition exceeding 

 this number by about 5,500,000 miles. 



In consequence of these varying distances, the apparent 

 size of his disc is undergoing changes ; thus the conditions 

 at each succeeding opposition are rarely the same. 



That the coming opposition is a very favourable one, 

 can be seen from the table given below, and that it will 

 be more favourable than that of 1892 for observers on 

 the northern hemisphere is due to the planet's more 

 northern declination at this period, bringing him 

 above the mists which spoil good seeing near the 

 horizon. 



Date of Opposition. i Semi-diameter. 



1862 October 5 



1S69 February 13 



1873 April 27 



1877 September 5 



18S1 December 26 



1884 lanuary 31 



1885 April 10 



1892 August 13 



1894 October 20 



Let us turn our attention now to the observations that 

 have been made up to the present time, and see what has 

 as yet been learnt from a study of the Martian surface. 

 The work to which we are now about to refer hails from 

 the Lowell Observatory, Flagstaff, Arizon.i, and the ob- 

 servations have been and are continually being made by 

 its founder, Mr. I'ercival Lowell, who has set his 

 observatory on this spot for the single purpose of care- 

 fully studying the surface of Mars during this period of 

 opposition. The old saying that the eaily bird gets the 

 first worm, can be applied with some force to Mr. 

 Lowell, for he has been rewarded with ample satisfaction 

 for coinmencing his observations at such an early date. 

 Indeed, perhaps the great value of this series of observa- 

 tions which he is making will be in its very length, for is 

 he not, from a study of his own observations, watching 

 attentively the various stages of a vast aquatic display 

 which becomes more and more distinct the nearer the 

 earth is approached, and therefore must be continually 

 and for a long period observed .' 



