384 



♦ KNOV/LEDGE ♦ 



[Dec. 28, 1883. 



Uustriated muscles are found in man and various animals 

 in the alimentary canal, bladder, ducts of glands, io. They 

 have been generally considered to consist of elongated cells, 

 but Professor Eugelmann states that smooth fibres are 

 really composed of fibrillse. 



They sometimes exhibit strise, and there is no liarsh and 

 absolute distinction between the two sorts. The charac- 

 teristic "vital property of muscular fibre," says Owen, " is 

 to alter under stimulus its relative dimensions of length 

 and breadth. When it becomes shorter and thicker, it is 

 said to contract, and by these contractions the movements 

 of the body and of its parts are produced." 



THE UNIVERSE OF SUNS. 



By E. a. Proctor. 



(Contimied from p. 370.) 



IN far better accordance with modern ideas, are the views of 

 the great astronomer Christian Huyghens, as expressed 

 in his fine work the " Cosmotheoros.* He held that the sun 

 is one of the stars and resembles tliem in size and structure. 

 The distribution of the stars he regarded as in a general 

 sense uniform, for he held that the same distance which 

 separates the sun from the nearest star separates that star 

 from the next beyond, that from the next, and so on to 

 infinity. We have already seen that his hypothetical study 

 of the universe led to researches and results of considerable 

 importance. 



We owe, however, to Thomas Wright, of Durham, the 

 first attempt to form a complete theory of the universe. 

 The Milky Way was not referred to at all in the speculations 

 of Huyghens, nor was the important position of the star- 

 cloudlets in theories of the Cosmos recognised in Huyghens' 

 time. Wright's views i-anged over the whole of the 

 sidereal universe as known in his day ; and we shall see 

 that by a bold effort of genius he anticipated the specula- 

 tions which the greatest of all astronomers based a few 

 years later on observation. 



Wright examined the structure of the Milky Way with 

 a reflecting telescope only one foot in length, satisfying 

 himself that the galaxy really consists of a multitude of 

 minute stars. Reasoning concerning the Milky Way, he 

 remarked that if we judge of it only by phenomena we 

 must regard it as a zone of stars surrounding the heavens. 

 But this conception of the !Milky Way as a perfect ring is 

 not in agreement with the irregular distribution of the 

 stars which do not lie upon the galaxy, but seem dispersed 

 promiscuously throughout the space surrounding us on all 

 sides. It seems inconsistent with the harmony observed 

 in " all the other arrangements of nature " that one 

 scheme of stars should be arranged with perfect sym- 

 metry, while another is scattered in-egularly. It is 

 far more reasonable to conclude — so Wright reasoned — 

 that the seeming incongruity is due only to the imperfect 

 nature of our survey both as respects the extent of space 

 and duration in time. " When we reflect,"! says Wright, 

 " upon the various configurations of the planets and the 

 changes which they perpetually undergo, we may be assured 

 that nothing but a like eccentric position of the stars 



* It is perhaps not very generally known that the Plumian Pro- 

 fessorship of Aitronomy at Cambridge was founded by Dr. Plumer 

 as an expression of the pleasnre he had derived from the perusal of 

 Huyghens* Cosmotheoros. The work was recommended to him by 

 Flamsteed, the first Astronomer Koyal. 



t I quote from an abstract of Wright's views in Grant's fine 

 *' Histon.' of Physical Astronomy." 



could occasion such confusion among bodies otherwise so 

 regular : in like manner we may conclude that as the pla- 

 netary system, if viewed from the sim, would appear perfectly 

 symmetrical, so there maybe some place in the universe where 

 the arrangement and motions of the stars may appear most 

 beautiful. If we suppose the sun to be plunged in a vast 

 stratum of stars of inconsiderable thickness compared with 

 its dimensions in other respects, it is not difficult to see 

 that the actual appearance of the heavens may be re- 

 united with a harmonious arrangement of the constituent 

 bodies of such a system with respect to some common 

 centre, provided it be admitted at the same time that the 

 stars have all a proper motion. In such a system it is 

 manifest that the distribution of the stars would appear 

 more irregular the farther the place of the spectator was 

 removed from the centre of the stratum towards either of 

 the sides. It is also evident that the stars would appear 

 to be distributed in least abundance Ln the opposite direc- 

 tions of the thickness of the stratum, the visual line being 

 shortest in these directions ; and that the number of visible 

 stars would increase as the stratum was viewt'd through a 

 greater depth, until at length, from the continual crowding 

 of the stars behind each other, it would ultimately assume 

 the appearance of a zone of light." 



It will be observed that Ln these words we have a com- 

 plete enunciation of what has been called the Grindstone 

 Theory of the stellar system. The theory is based by 

 Wright on observed facts precisely as it was afterwards 

 based by Sir W. Herschel on other observed facts. What- 

 ever credit appertains to the invention of the theory should 

 in justice be ascribed to Wright, who thus, in 1 750, reasoned 

 out and clearly described the views to which Herschel was 

 led in 1784. Wright did not convince his contemporaries, 

 but their slowness of apprehension seems to aflbrd no just 

 ground for depriving him of the credit due to his sound 

 analysis of known facts. 



Wright further held that the Milky Way is only one of 

 many systems of stars ; though the other systems form- 

 ing with our galaxy a system of star-systems, may not 

 resemble the galaxy or each other in structure. There 

 may be diflerences as striking as those which exist 

 between the rings of Saturn and the belts of .Jupiter. 

 " Some systems of stars may move in perfect spheres, at 

 different inclinations and in different directions ; others 

 again may revolve like the primary planets in a general 

 level ; or more probably in the manner of Saturn's 

 rin^ ; nay perhaps, ring within ring, to a third or fourth 

 order." 



Wright believed that the common centre around which 

 the stais of the galaxy travel is an orb larger and more 

 massive than the rest He also considered that there are 

 sidereal systems within the boundaries of the visible uni- 

 verse, and subordinate to the great system of the Milky 

 Way. It is to such parts of the Milky Way that he refers 

 when he speaks of " the immensity of space being occupied 

 by an endless succession of systems, analogous in their 

 structure to the great system " (the Milky Way) " of which 

 the visible universe is composed (and of which thej' form 

 part)." This seems clear from the way in which he reasons 

 respecting other Milky Ways. For, referring to the theory 

 that such systems exist, he remarks : — "That this in all 

 probability may be the case is in some degree made evident 

 by the many cloudy spots, just perceivable by us, as far 

 without our starry regions, in which, althougli visibly 

 luminous spaces, no one star or particular constituent body 

 can possibly be distinguished fhe.^e, in all likelihood, maij 

 he external creations, horderiny uj)07i the known one, too 

 remote for even our telescopes to reach." 

 (To be continued.) 



