132 



KNOWLEDGE. 



[June 1, 1900. 



PHOTOGRAPHS OF THE NEBULA M. 8 

 SAGITTARII AND OF iji VI. CETl. 



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



NEBULA M. 8 SAGITTARII. 



R.A. 17h. 57m. 33s. Decl. 24° 23'0 South. 



The iihoto^raph was taken with th" 20-iuch refiector on 

 the 11th July, 1800, between, sidereal time, 18h. 2ni. and 

 lOh. 32m., with an exposure of the plate during ninety 

 minutes. 



Scale — one millimetre to twenty-four seconds of arc. 



The nebula is referred to in the jSf.G.C. No 6523, G.C. 

 43(il. h 3722. 



The photograph shows it to be a cloud of nebulous 

 matter extending in north follotviny to south prerediiii/ 

 direction forty-eight minutes of arc, and about the same 

 extent in south foUowiny to north preceding. Near the 

 2>recediufi end the nebulosity is dense, with a bright star 

 apparently touching the margin, and giving it, on the 

 negative, the appearance of an eye on one side of which is 

 a prominent space free from nebulosity ; there are also 

 extensive spaces in some parts of the nebula which are 

 almost free, and some rjuite free, from nebulosity ; these 

 give it a structural ajipearance. 



There are many stars of between 8th and 1 7th magnitude 

 either involved or seen in projection upon the nebula, and 

 on the following side they resemble a cluster of bright 

 stars, but I do not think they are physically connected 

 with it ; they are probably between the earth and the 

 nebula. 



The place we should, with our present knowledge, assign 

 to this nebula in the order of stellar evolution, would be 

 an early state pjrior to a spiral formation. 



But we must have patience as well as moderation in our 

 speculations, for millions of years will probably elapse 

 before it is completely develoi)ed into a cluster of stars. 



NEBULA y VI. CETI. 

 R.A. Oh. 42m. 36s. Decl. 25° 50'-6 South. 



The photograph was taken with the 20-iuch reflector on 

 the 25th December, 1809, with an exposure of the plate 

 during ninety minutes. 



Scale — one millimetre to twenty-four seconds of arc 



The nebula is referred to in the N.G.C. No. 252, G.C. 

 138, h 61=2354, and is figured by Herschel in the Phil. 

 Trans., 1833, PL 14, Fig. 52, p. 495. Also by Lassell iu 

 the Mem. B.A.S., Vol. XXXVI., PI. 1, Fig. 1, p. 40. 



The photograph shows the nebula to be a spiral viewed 

 at an acute angle. It measures twenty-four minutes of 

 arc in diameter, which is in the direction north j^ireceding 

 to south following, and is studded with numerous conden- 

 sations of a stellar character ; there are also six stars, of 

 the normal tyi)e, wliicli are probably seen in projection 

 upon it. These, together with the stellar condensations, 

 will afford reliable fiducial points for the measurement 

 from other stars around the nebula with the object of 

 detecting any movements either of rotation or of transla- 

 tion that may in future take place in it. 



Both these nebulte are between twenty-four and twenty- 

 six degrees of south declination ; they can therefore be 

 photographed under much more favourable conditions in 

 (ibservatories near, or to the south of the equator, and 

 tliere can be no doubt that Dr. Gill at the Cape, or Prof. 

 Pickering, will give a good account of them. 



If we consider the nebula Ijl VI. Ceti with reference to 

 the evolution of stellar systems its place would be far in 

 advance of M. 8 Sagittarii. In this the convolutions are 

 not only formed but the development of the stars in them 



has also reached an advanced state ; some of them appear 

 like small well-formed nebulous stars; and the nebula in 

 time — who can imagine how long — will appear as a star- 

 cluster, and resemljle those which have already been photo- 

 graphed and described in the volumes of "Photographs of 

 Stars, Star-Clusters, and Nebulae." 



ASTRONOMY WITHOUT A TELESCOPE. 



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



v.— OBSERVATIONS OF THE SUN. 



It may seem at first sight a useless and idle suggestion 

 that beginners in Astronomy should set themselves to 

 the redetermination, on the roughest scale and with the 

 simplest of instruments, of astronomical constants which 

 were first determined more than five millenia ago, and 

 which are now ascertained in our modei^n observatories 

 to an almost inconceivable degree of exactness. Yefc if 

 we think for a moment we shall see that this is but the 

 method which experience has taught us is the most 

 effective in learning the other physical sciences. We 

 know perfectly well wc can never make a chemist of a 

 boy by giving him a course of chemical text^books. We 

 set him to repeat for himself experiments which were 

 first made in the very infancy of the science. We make 

 him determine again the combining weights of different 

 elements, though these are known far more exactly than 

 he can possibly work them out ; and in so doing, he not 

 only acquires skill as a worker, but the subjects of his 

 study become real to him ; he learns to know them in 

 a sense which no amount of reading about them could 

 ever supply. 



It has been the drawback of Astronomy that this 

 course has so seldom been adopted, and the inevitable 

 result has been seen in that no science whatsoever has 

 produced so large a proportion of paradoxers and cranks. 

 There is no science, the chief facts of which are so widely 

 disseminated ; there is none of which those facts are so 

 little known by practical personal observation. 



Much of this unfoi-tuuate state of things is due simply 

 to the modern tendency to live in towns. Here the 

 smoky atmosphere dulls the shining of the heavenly 

 bodies ; the crowded buildings hide the horizon and 

 curtail the view of the sky, and at night the ai'tificial 

 lights in streets and houses completely di'own the feebler 

 glitter of the stars and draw off attention from them. 

 We do not need moon and stars as our ancestors 

 did, and therefore we do not notice them. We 

 do not need to observe the sun to give us the time 

 of the year; our almanacs tell us that. Therefore, 

 except in observatories, the sun's place in the heavens 

 remains unnoted. 



But in early times this observation was of the very 

 first importance. The constellations as wo have seen, 

 were mapped out some 5000 years ago. (Knowledge, 

 Februai-y, 1900, p. 37.) Before that was done^ — how 

 long before we cannot tell — the length of the year had 

 been determined and the appai-ent path of the sun 

 amongst the stars had been laid down. The exact 

 methods and instruments those early astronomers em- 

 ployed are not recorded, nor, if they were, would there 

 be any reason for slavishly copying them in repeating 

 the work to-day. But in all piobability the first a.s- 

 tronomical instrument was one of Nature s own pro- 

 viding, the natural horizon. And wherever a fairly 

 good one is available, the beginner in astronomy is 

 strongly recommended to make use of it. 



If this were so then no doubt those primeval observers 



