Fkbbcary 1, 1900.] 



KNOWLEDGE. 



35 



similar apparatus on the hind leg, but the femur is not 

 nearly so thii-keued ; it is armed with shai-pcr spines 

 than S. pipiens, and the tibia is furnished with a similar 



Fio. 9.— "Claspcr" of mule Fio. 10. — "Holding organ" of male 

 S. pipiens. x KXl diametors. .S. jjipiens. x 27.") diamoters. 



process, though not quite so continuous. The explana- 

 tion of these variations forms an interesting problem, 

 which with opportunity for observation, I do not think 

 is incapable of elucidation. 



In conclusion it is my duty and my plea-sure to ex- 

 press my obligations to Mr. E. Austen, of the British 

 Museum, for information on the life-history, literature, 

 and the kind gift of specimens of S. pipiens. 



¥ 



PHOTOGRAPH OF THE TRIFID NEBULA 

 IV. 41 SAGITTARII, AND OF THE REGION 

 SURROUNDING. 



By Isaac Roberts, d.sc, f.r.s. 



The photograph annexed is of the region in the 

 sky comprised between R.A. 17h. 54m. 12'8s. and R.A. 

 17h. .58m. 421s., and in declination between south 

 23° 37'-6 and 22' 16'-6. The area, therefore, is 4m, 29:3s. 

 in extent from following to preceding, and 1° 21' from 

 north to south. Scale— one millimetre to twenty seconds 

 of arc. 



Co-ordinates of the fiducial stars marked with dots for 

 the epoch 19<j0. 



star (.) D.M. Schunfeld No. 450.3 Zone - 22° E.A. 17h. 55m. 50 R'. 



Dec. S. ±J=> «'•!. Miic. fiO. 

 Star (.,) D.M. No. 4533 Zone - 22° E.A. 17h. 57m, 53-6s. Dec. S. 22° oO 7. 



Maj. 7-4. 



The Trijid nebula ^ IV. 41 is in R.A. 17h. 56m. ; 

 declination, south 23° 2'. 



Refeeences. 



N.G.C. No. 6514. G.C. 4355. h 1991 = 3718. Phil. 

 Trans., 1833, PI. XVI., Fig. 80. Cape Ohs., PI II., Fig. 2. 



The photograph was taken with the 20-inch reflector, 

 and exposure of the plate during 90 minutes, on the 

 13th July, 1899 ; and it will be observed that the nebula 

 is characterized by tortuous dark rifts without stars 

 in them. Those which intersect the denser part of the 

 nebulosity have margins sharply defined, whilst those 

 in the fainter parts are broader, with the margins less 

 defined and some nebulosity in the rifts. 



There have been published in Knowledge, during 

 the past two years, three photographs showing the 

 densely dark rifts, and besides those, others showing 

 the broader rifts ; amongst the latter the nebulae in 

 Orion and in Andromeda are conspicuous examples, as 

 well as those of the cloud-like class. 



The inferences we may reasonably draw from these 

 aijpearances are that those nebul;v> are developing into 

 the more stable form of stars by the influence of gravi- 

 tation. They appear to bo the earlier stages in the 

 development of spiral nebula', examples of which have 

 been shown on many photographs already published, 

 where it wa.s obvious that tlio nebulosity is aggregatin;^; 

 into stars in the convolutions. 



The most useful work that can now be done for the 

 advancement of astronomical science is the careful 

 measurement of tho position angles and distances of 

 the sufficiently well defined star-like condensations of 

 tho nebulosity in these vai'ious nebula} from selected 

 normal stars, six or eight in number, which surrolind 

 the respective objects within tho radius distance of one 

 degree or less. In this way astronomers would, within 

 an interval of a few years, bo able to demonstrate tho 

 changes that have taken place in these bodies with 

 reference to those stars as fiducial points; and thus 

 positive knowledge would bo gained in place of the 

 speculative with its never ending controversy. 



It is welcome intelligence that Dr. Drcycr, of the 

 Armagh Observatory, is about to commence the attack 

 upon this work. 



♦ 



ASTRONOMY AND ASTROLOGY; A QUESTION 

 OF PRIMOGENITURE. . ; 



By E. Walter Maunder, f.r.a.s. ', 



No record exists to tell us under what circumstances, 

 and exact form, the science of Astronomy had its first 

 beginning. We can, therefore, but make a guess as to 

 its origin, and most of our leading writers are a,t one as 

 to the agent which gave it birth. Astronomy, say they, 

 is the daughter of Astrology. 



It may seem presumptuous to call in question an 

 idea which writers, of such sound judgment and keen 

 perception as the late R. A. Proctor, have regarded as 

 axiomatic, but, in my own view, Astrology, so far from 

 being the parent of Astronomy, must be looked upon 

 as a late and most degenerate descendant from the sub' 

 lime science. 



Astronomy, like everything else, had a beginning-. 

 There must have been a time when men had not yet; 

 discovered that the stars seen on one evening held the 

 same lelativ© positions as those obsei-ved the next; « 

 time viflien no planets at all had been recognised, and 

 when the sun and moon were not thought to be of 

 the same order as the other heavenly bodies. 



An unintelligent townsman of to-day, who may perr 

 chance find himself out in the country on some dark; 

 clear, night, looks up and remarks casually, that " It 

 is a lovely night," and " What a lot of stars there are 

 out," and there his knowledge and recognition of the 

 spectacle end. He knows ho constellations, he recog- 

 nises no particular stars ; he has never watched the 

 heavens long enough to discern that they are continually 

 turning round the pole ; a planet and a fixed star are 

 both alike to him ; the heavens present no problems, 

 give no information to him. 



Now this state of things, which we find only too 

 widely prevalent to-day, much to ^ho discredit of our 

 modern civilization, must once have been universal. 

 There was a time when no one could recognise 

 a constellation, because none had yet been mapped out j 

 when none could tell tho difference between a pla'nefc 

 and a fixed star, because no observations had at that 

 early' date been devised for following the rtoveftieilt 

 of the one, or proving the iinmobility of the other. 



