Fbbeuary 7, 1902.] 



SCIENCE. 



221 



this rapidly accumulating material and to 

 present its substance in untechnical form 

 merits the thanks of both professional and lay 

 readers, even though occasional inaccuracies 

 or omissions aifect the text or the rapid ad- 

 vance of knowledge renders obsolete some pas- 

 sages before the ink is dry upon the pages. 

 A double acknowledgment is due when, as in 

 the present case, that author is the one astron- 

 omer marked oiit by long and distinguished 

 service in important parts of this field as pecul- 

 iarly adapted to the task. The title. Retired 

 Professor TJ. S. Navy, that follows the author's 

 name upon the title page, suggests thoughts far 

 from complimentary to that fatuous govern- 

 mental policy in accordance with which as- 

 tronomers are retired from the public service 

 upon reaching an age limit not far removed 

 from the maximum of intellectual power. 



In substance, though not in formal arrange- 

 ment, the present work falls naturally into 

 two parts; first, a description of methods of 

 research and such elementary classification of 

 stars as are the familiar province of the better 

 text-books, e. g., the grouping of stars into 

 constellations, the explanation of stellar mag- 

 nitudes, proper motions, parallaxes, stellar 

 spectroscopy, the description of the phenomena 

 presented by variable and double stars, 

 nebulse, etc.; and second, a more original part 

 devoted to the larger problems of stellar dis- 

 tribution, the significance of the milky way, 

 the sun's motion, stellar evolution and sim- 

 ilar matters which may be grouped, fairly 

 enough, under the title, the structure of the 

 heavens. We welcome here a presentation of 

 some of Kapteyn's results not hitherto acces- 

 sible, of Huggins's views of stellar evolution, 

 and the author's own methods, inferences and 

 conclusions from the new material collected 

 and sifted in the preparation of this work. As 

 types of these last-named categories it is in- 

 teresting to note the simple statistical method 

 (p. 300) by which certain results first obtained 

 by Kapteyn through an elaborate and tedious 

 mathematical process are independently de- 

 rived. Of a very different order is the sug- 

 gestion made with reference to Bailey's dis- 

 covery of variable stars in clusters, that there 

 is 'a strong presumption that the variations 



in the light of these stars are in some way 

 connected with the revolution of bodies round 

 them, or of one star round another.' The dis- 

 tribution of the stars in space is treated with 

 a fullness of detail that occasions some sur- 

 prise at the almost complete neglect of a pos- 

 sible absorption of starlight in the interstellar 

 spaces; a possible defect of transparency in 

 the celestial void, that has been rendered a 

 classic theme by Struve's speculations and 

 more recently has been elaborated by Schiapa- 

 relli. 



Taken as a whole the work contains in ex- 

 cellent form a large amount of material inter- 

 esting to the professional astronomer and in 

 even larger measure valuable to the popular 

 expositor of astronomy, teacher, lecturer or 

 writer. As it is sure to be largely drawn upon 

 by this class it seems important to eliminate 

 as rapidly as possible those errors and inac- 

 curacies inseparable from a first edition, 

 among which we note the following: 



P. 158, line 10, for eleven read five and 

 one-half. 



P. 182, line 3, for Triphid read Trifid. 



P. 194, insert a^ in the numerator of the 

 fraction. 



P. 198, line 1, for 2m read 2™. 

 The statement made on p. 179 with regard 

 to the Orion nebula, 'This is plainly visible 

 to the naked eye and can be seen without diffi- 

 culty whenever the constellation is visible,' 

 does not at all correspond to the experience 

 of the present writer who has great difficulty 

 in seeing the nebula with unaided vision, even 

 under favorable circumstances, and whose ex- 

 perience is shared by a dozen young people, of 

 both sexes, who at his request have looked for 

 the nebula. 



In the matter of nomenclature some objec- 

 tion may fairly be raised to the apparently 

 needless introduction of new terms in place 

 of the familiar old ones, such as the logically 

 inappropriate, apocenter, pericenter, for apas- 

 tron, periastron, in connection with double 

 star orbits, and the rechristening of the Praun- 

 hofer lines of the solar spectrum as Wollaston 

 lines. But with all due allowance for such 

 minor blemishes the book remains in its en- 

 tirety a notable contribution to the literature 



