118 



KNOWLEDGE. 



[May 1, 1897. 



very exceptional. The motions of the stars which I cited 

 in my former letter are mucli in excess of the usual 

 amount. Those of the above five stars are not so. 



The best apircemeut is perhaps that determined by Vogel 

 for the velocity in the line of sight. It does not, however, 

 include S; and for yj Ursas ]\Iajoris (which admittedly docs 

 not belong to the system) he determined -IC-S. The 

 motion of 5; is R.A. —0 0104, Decl. —0019. 



I am not aware of the proper motion of Alcor, but 1 

 would expect to find that it agreed closely with that of 

 s Ursic Majoris, and that a physical connection existed 

 between the pair. But this would afford no ground for 

 including j3, y, S, and s in the same system. 



It is favourable to the theory of a physical connection 

 between these five stars that they all present the same 

 kind of spectrum, A. But here, again, 1; presents the 

 spectrum A also; a, on the other hand, has the spectrum K, 

 and less than half the velocity in the line of sight of the 

 other six. W. H. S. Monck. 



*-^^ 



THE CHEMISTRY OF THE STARS. 

 To the Editors of Knowledge. 

 SiKs, — In your last issue Mr. Maunder mentions some 

 facts which he believes to be adverse to the hypothesis of 

 the uniform chemical constitution of the heavenly bodies, 

 but to my mind, at least, they are not inconsistent with 

 such a view. The idea that difference of temperature is 

 the fundamental cause of differences in stellar spectra does 

 not necessarily involve the supposition that each star must 

 pass through stages represented by every one of the 

 " peculiar spectra " which has been observed. Pickering, 

 for example, has shown that some of these exceptional 

 spectra are composite, the components representing stars 

 of different ages, and such a compound spectrum would 

 not be put on by single stars. Other special variations of 

 spectrum, due to the interaction between two bodies in 

 close proximity, are not inconceivable, and, in fact, are 

 probably revealed to us in many variable stars. 



Again, there appears to be no sutHcient reason why the 

 peculiar distribution of the bright-hne stars should not 

 indicate a ring of stars of equal temperature. This is at 

 least as easy to conceive as a ring of stars of unusual 

 chemical composition. 



Coming now to the objection that in the Milky Way 

 large and small stars of apparently the same type are 

 associated, it is necessary to state that a great variety of 

 spectra has hitherto been very commonly included in the 

 same spectral type. For instance, all stars with well- 

 developed hydrogen lines are classed together by those 

 who still hold to Secchi's classification, although 

 individual spectra may be very different. Not having 

 given special attention to the stars of the Milky Way, I 

 am unable to say whether the supposed identity of the 

 so-called " first type stars " of different magnitudes 

 composing it is really established, but I do not think the 

 pubhshed accounts of the spectra are sulliciently detailed 

 to permit a trustworthy conclusion to be drawn. But 

 there is another point. The period required to produce 

 spectral modifications great enough for detection must be 

 of very considerable duration, so that stars of unc(]ual 

 masses in the same part of space may appear to be at 

 practically the same spectral phase at a gi\eu time, 

 although the smaller may in reality be further advanced. 

 The apparent identity of bright and faint stars of the 

 Pleiades group may similarly rest upon inconclusive data, 

 but, as JjQckyer has pointed out, the fact of these stars 

 being involved in nebula' offers another explanation. 



With regard to the last point which Mr. Maunder 

 suggests for my consideration, 1 would only say that to 



deny the similarity of chemical composition of nebuhe and 

 stars is to deny the possibility of nebulu' and stars having 

 any connection at all. 



Making due allowance for our fragmentary knowledge, 

 I still think that the spectroscopic phenomena presented 

 to us by the heavenly bodies do not clash with the view 

 that their chemical composition is uniform. 



A. FoWXEll. 



[Mr. l''owler has evidently missed the point of the last 

 paragraph of my note on page 99. If some vast nebula 

 crystallizes out into a number of stars, then, unless the 

 nebula be strUih/ /lomdiiciicinis. thrawiliout, the discrete stars 

 formed from it must vary in their composition, which 

 must in each case correspond to that of the particular 

 region of the nebula from which each one was severally 

 formed. Mr. Fowler's penultimate paragraph does not 

 appear to me to have any relation to my suggestion. It is 

 one thing to admit that the chemical composition of nebulre 

 is on the average similar to the chemical composition of 

 stars ; indeed, the matter is beyond contention. It is a 

 wholly different thing to assert that all nebula- are of the 

 same proportionate composition, and are all strictly 

 homogeneous throughout. — E. Walter Maunder.] 



ON THE VEGETATION AND SOME OF THE 

 VEGETABLE PRODUCTIONS OF AUSTRAL- 

 ASIA.-II. 



By W. BoTTiNG Hemsley, F.R.S., F.L.S. 



THE popular impression respecting the Australian 

 flora is that it contains comparatively few plants 

 yielding products of economic value, and this is a 

 correct impression so far as edible fruits and vege- 

 tables are concerned ; but it should be remembered 

 that this is true of most countries. Fruits and vegetables 

 that come to our tables are the result of long generations 

 of cultivation. Take the crab, carrot, parsnip, celery, or 

 almost any of our fruits or vegetables in a wild state, and 

 we should get very little satisfaction out of them. This, 

 however, is a little digression. Australia is by no means 

 poor in vegetable products, and other countries have been 

 greatly enriched by importing and cultivating some of 

 them. This is notably the case with regard to the gum 

 trees. I have already mentioned that the expeditions of 

 Dampier and Cook revealed the existence of gum trees in 

 both Western and Eastern Australia, but neither expedi- 

 tion entered the country sulliciently far to discover the real 

 forests. Everybody has heard or read of the gold mines of 

 Western Australia — of Coolgardie and that region — but few 

 persons in this country have seen or heard of the recent 

 report of the Conservator of the forests of that par': of the 

 world. A glance at the illustrations in that report would 

 astonish anyone acquainted only with the forests of Europe, 

 for they equal, if not in some respects surpass, the 

 coniferous forests of North America. Mr. J. Ednie-Brown, 

 the author of the report in question, has been successively 

 Ciovernment Conservator of Forests in South Australia, 

 New South Wales, and Western Australia, and therefore 

 writes with great authority on his subject. He states that 

 there are forty-seven million acres of land in Australia 

 upon which useful marketable timber is growing, and that 

 there are six hundred different species or kinds of timber 

 trees in Australia! In his enthusiasm, Mr. Ednie-Brown 

 has included a largo number of trees that do not yield 

 timber of any appreciable commercial value ; but even if 

 we reduce the total by one-half, what a contrast as com- 

 pared with the richest forest distiicls of the northern 



