8 



DlSCcni.HY 



would increase not giiulually, but suddenly near the 

 boundary of the ring. " The Milky Way," said 

 Seeliger, " is no mere local phenomenon, but is closely 

 connected with the entire constitution of our stellar 

 system." Seeliger, in thus emphasising the funda- 

 mental imp)ortance of the galactic zone, was led nearer 

 to the standpoint of the elder Herschel. 



At the close of the century, several estimates had 

 been made of the possible extent of the stellar universe. 

 Wlien the original disc-theory was propounded by 

 Herschel, the actual distances of stars were unknown ; 

 but he assigned to the universe in its greatest extension 

 a diameter 850 times the mean distance of stars of the 

 first magnitude — the thickness of the disc, in the 

 direction of the galactic poles, being 155 of these units. 

 More definite estimates were possible after the measure- 

 ments of stellar parallaxes had indicated the scale on 

 which the universe is built. Newcomb, in 1901, 

 estimated the distance of the stars at the boundary of 

 the universe as 3,000 light-years ' ; and as the sun was 

 believed to occupy a fairly central position, this 

 indicated a diameter of 6,000 light-years. Seeliger, on 

 the other hand, placed the limits of the universe at 

 9,000 light-years from the sun, the diameter being 

 about 18,000 light-years. More modest estimates were 

 adopted by other competent authorities. 



At the close of the century, it was believed to be 

 definitely established that all the star-clusters and 

 nebulae were situated within the stellar universe. The 

 " island universe " theory which Herschel put forward 

 as the corollary to the disc-theory, but afterwards 

 virtually abandoned, appealed to the imagination, and 

 retained its place for many years in popular volumes on 

 astronomy. But it did not survive the vigorous 

 criticism of Proctor, Gore, and other writers. Its 

 partial revival during the last decade has been one of 

 the most remarkable features of modern astronomy. 



The problem of the construction of the universe may 

 be attacked from three different standpoints — stellar 

 distribution, motion, and distance. The earlier astrono- 

 mers were forced to concentrate on ascertaining the 

 facts of stellar distribution, and had to be content with 

 deductions from these facts. Even down to the close of 

 the nineteenth century, the known motions and distances 

 of the stars were too few and in many cases uncertain 

 to warrant the formulation of a hypothesis based upon 

 them. Madler, it is true, made a bold attempt to 

 locate the centre of the sidereal system from a dis- 

 cussion'of proper motions, which seemed to point to 

 Alcyone, the chief star of the Pleiades, as the centre of 

 the universe ; but his lailure indicated clearly that the 

 time was not ripe for such generalisations. The 

 twentieth century, however, has witnessed a remark- 



AMight-year is the distance travcUnd by light in a year. 

 Light travels at the rate ot 186,000 miles per second. 



able extension of our knowledge of the stellar system. 

 Not only have the refined measures of parallax and of 

 proper and radial motion made during the second half 

 of the last century contributed to this, but new methods 

 of measuring the absolute magnitudes of individual 

 stars and of stars in clusters have been devised, and from 

 these measures the distances of large numbers of 

 celestial bodies have been computed. To a considera- 

 tion of these recent advances and discoveries a second 

 article will be devoted. 



Note. — A bibliography will be given next month. The best 

 book on this part of the subject is that by the author on 

 Herschel (S.P.C.K., li. and 2S. t>d.), from which, by kind per- 

 mission, the photo of Herschel is reproduced. — Ed. 



The Discoveries in Crete 



By George Glasgow, B.A. 



(Continued Jrom October No., p. 316) 



VHI 



The Cretans had a system of writing as long ago as 

 2500 B.C. The language therein embodied is still a 

 mystery to us, in spite of Sir Arthur Evans's monu- 

 mental work Scripta Minoa (1909). One hopes that 

 in a further volume Sir Arthur may have found a 

 clue to the mystery, but up to the present the bleak 

 fact remains that there is no adequate starting-point 

 for any attempt at interpretation. If only a bilingual 

 inscription could be found — a Cretan document, that is, 

 side by side with a translation in some known language 

 such as Egyptian — a start could at once be made. 



It was inevitable that the art of writing should be 

 evolved early in the history of man. Even in the 

 most primitive stages of life there would be the elemen- 

 tary necessity, for instance, of identif\"ing one's own 

 property, and for this the most likely means would 

 be some system of marking. Then, again, the develop- 

 ment of communal life would entail the duty of keep- 

 ing appointments, or of doing a particular thing at a 

 particular time. It would, one thinks, have been 

 too much of a strain, even for the mind of a Stone Age 

 man, to keep all the details of his daily, still more of 

 his annual, routine in his head, and the handkerchiefs 

 of those remote days (assuming, as one must, that they 

 had any) may not have been of such a material as to 

 lend themselves readily to mnemonic knots. It is 

 quite conceivable, as an instance of the sort of neces- 

 sity that would arise, -that at a given time it could be 

 calculated how many days ahead the provisions in 

 hand would last, and when, therefore, the hunter must 

 be ready for the hills. He might prepare a handy 

 reminder by roughly drawing a spear-head, say, 

 together with a jiictographic representation of some 



