November 27, 1885.] 



SCIENCE. 



48: 



skilfully analyzed to prove that no Europeans, ex- 

 cept possibly Spaniards or Portuguese, can be ac- 

 climated in the zone lying between the isotherms 

 twenty-five degrees north and south of the equa- 

 tor. Of the French colonies, Algiers and New 

 Caledonia are the only ones not situated within these 

 limits. Fi'om every point of view, the French 

 colonial poUcy is shown to be disastrous. Neither 

 the French race or language can thus hope for ex- 

 pansion. Even commercially it is a failure, for 

 foreign nations can undersell France in her own 

 colonies. French emigration is always fatal when 

 it is perpendicular instead of parallel ; and there can 

 be no national advance until an intensive colonial 

 culture be substituted for the extensive system so 

 popular in this day. The work has many inter- 

 esting points for the ethnologist to consider, such 

 as the relations of European colonists with indi- 

 genous races. It is written with much force and 

 even grim humor, as when the author, after 

 analyzing the statistical situation of Algiers, sums 

 it up with the picture of the twenty-five thou- 

 sand productive colonists, each seated on four 

 graves, and guarded by a brace of soldiers. 



These two books are suggestive not only for 

 their political philosophy of freedom, but also as 

 fiurnishing clear and forcible views of the diffi- 

 culties which stand in the way of French progress. 



STARS IN RAPID MOTION. 



The small value of the parallax of 40 o^ Eridani 

 {Science, vi. 358), combined with its large proper- 

 motion (4'MO), brings it into prominence as the 

 third or fourth of the stars, moving rapidly across 

 our line of sight. Since a list of these stars seldom 

 appears in works on popular astronomy, we give 

 below the proper-motions //, the parallaxes tt, and 

 the resulting velocities v, in miles per second 

 across om- line of sight, of the eight stars which 

 head the Ust in the order of velocities. The 

 method of deriving the velocities is of course 

 very simple. If a star's annual proper-motion 

 equals its paraUax, it moves across our line of 

 sight each year a distance equal to the semi- 

 major axis of the earth's orbit. (How much it 

 moves to or from us can only be told by the spec- 

 troscope.) Therefore, since this motion increases 

 directly as fi, and inversely as tt, we have for the 

 annual motion across the line of sight — 



V t z= a^^ 



TT 



or, calling a 92.5 mUHon miles, and t the number 

 of seconds in a year, we have for the velocity in 

 miles per second — 



V = 2.93^' 



TV 



Of course, the proper-motions below are much 



more accurately known than the parallaxes, and 

 where the latter are small the values of v are cor- 

 respondingly uncertain. The authorities for the 

 adopted values of tt are given in the column 

 following them. In the case of 40 o^ Eridani, we 

 have weighted Gill and Hall 2 and 1 respectively, 

 as the former determination was made under 

 much the more favorable conditions, and rests 

 upon two comparison-stars. The latest values of 

 Hall and Ball for 61 Cygni are practically identi- 

 cal. The probable errors of all the values of - 

 are generally less than 0''.02. 



Star's name. 



M 





Parallax. 





77 



Authority. 





Groombridge 1830.... 

 Lacaille 9353 



7". 05 

 6 .96 

 4 .10 



3 .10 



4 .68 



4 .40 



5 .23 

 4 .75 



0".09 

 0.285 

 .185 

 .14 

 .22 

 .27 

 .48 

 .50 



Briinnow . 



Gill 



Gill and Hall 



Elkin 



Gill and Elkin 



230 

 71 



40 o2 Eridani 



e Eridani 



e Tndi 



65 

 65 



Lalande 21358 



48 



61 Cygni 



Hall and Ball 



Winnecke 



i\?. 



Lalande 21185 



28 



The first will be recognized as Newcomb's 

 'runaway star,' so graphically described in his 

 ' Popular astronomy;' but it will be seen that the 

 others have velocities which are at least com- 

 parable w^ith that of Groombridge 1830, and 

 indicate momenta that represent vast amounts of 

 energy. The discovery of huge suns like our own 

 rushing through space with these great velocities 

 is a matter of more than usual interest just now, 

 from the fact that Mr. Denning's claimed dis- 

 covery of fixed meteor-radiants has raised the 

 question as to the possible existence of broad 

 swiftly flying streams of meteorites in inter-stellar 

 space, moving with velocities entirely beyond the 

 control of our sun, and so broad that it takes the 

 solar system some years to pass through them. 

 (An annual parallax of 1° in a meteor-radiant cor- 

 responds to a velocity of over 1,000 miles per 

 second for the meteor-stream.) The idea of such 

 streams moving with such velocities is a startling 

 one, and, if shown to be true, gives a very vivid 

 idea of the forces acting, or which have acted, in 

 stellar space. It seems at first highly improbable 

 that such can be the case, but with the hard facts 

 of Groombridge 1830, and these other swiftly fly- 

 ing suns staring us in the face, the idea is worth 

 considering, at any rate. If these suns are the 

 products of condensation due to central atti-action, 

 so that the luminous energy by which they rcA'eal 

 themselves to us was once energy of translation, 

 it is no violent assumption to suppose that some 

 of their constituent parts were once moving with 

 much greater velocities than that of the present 

 whole. In fact, the man who should claim as a 



