232 



KNOWLEDGE. 



[December 1, 1891. 



photograph of the Sagittarius region. The picture of the 

 Sagittarius region on our second plate does not show 

 Mr. Fiarnard's dark arch as well as the pictures published 

 with the August number of Knowledge, 1890, or the 

 denser pictures published in the " Old and New Astro- 

 nomy," plate xxviii, but there is no doubt about its 

 existence, or the existence of the prominence-like 

 structures which spring from its eastern or convex side. 

 As remarked by Mr. Barnard in the paper accompanying 

 his photographs (published in the Monthhj Xoticca, vol. L., 

 p. 314), this dark lane or arch amongst the stars seems 

 to be intermediate in distance between the different bright 

 structures shown upon the plate. It evidently lies in 

 front of the bright structures shown on the lower and 

 upper parts of the plate, and seems to be crossed or broken 

 in upon by one of the bright structures at A'. 



Fig. 5 is an index map which indicates the position of 



"^A' 



Fig. 5. — Diagi'ain indicating the position of dark tree-like 

 structui'es ti-aceable on Mr. Barnard's photogi-jipli of the 

 Sagittarius region. 



two dark tree-like structures, C and B, which both seem 

 to spring from the dark region D at the bottom of the 

 Sagittarius plate. From this same region also springs the 

 bright tree-Uke structm-e indicated in outline in Fig. 6. 

 The dark structvu-e C seems' to lie in front of the bright 

 tree-like form shown in outline in Fig. 6. This bright 

 tree-like form, as well as the dark structures B and C, all 



■•-; 



seem to have had their 

 origin in the dark region 

 D, and to indicate the 

 existence of colossal out- 

 rushes of matter into a 

 resisting medium. 



Like the comparatively 

 small dark structure indi- 

 cated in Fig. 1, these larger 

 dark structures seem to be 

 associated with bright stars 

 which lie along their borders, 

 though the stars are not 

 arranged in such definite lines 

 or streams along the edges of 

 these large dark regions as they 

 are along the borders of the 

 narrow dark channels, and 

 smaller tree-like structures 

 such as that shown in Fig. 1 

 and at the summit of C, 

 Fig. 5. It win be noticed also 

 that the dark region at the 

 bottom of the plate is bordered 

 by two conspicuous star clus- 

 ters. The dark regions in the 

 trifid nebula are also bordered by lines of stars, and the 

 dark patches or holes in the Milky Way, referred to in the 

 October number (a striking example of which is shown in 

 Mr. Barnard's photograph), are surrounded by circles of 

 stars. It is e\"ident that there must be some intimate 

 connection between the dark regions, or the absorbing 

 matter they contain, and the stars surrounding them. In 

 the case of the solar prominences we know that the tree- 

 like forms are due to masses of glowing gas shot upward 

 into a resisting medium ; and it seems very probable that 

 the tree-hke structures of the Orion nebula also consist of 

 gaseous matter, for they are the brightest parts of the 

 nebula, and the spectroscope shows that the chief jmrt of 

 the light of this nebula is emitted by incandescent gas. 

 Have we, in the Milky Way, gaseous phenomena on a still 

 more colossal scale ? 



structure, visible 



graph of theSagittarius region. 



photo- 



Notices of Boolts. 



I'riinitiir Folk. By EUe Eeclus (Walter Scott). — In 

 this volume of the " Contemiiorary Science Series" we have 

 an intensely interesting description of (he manners and 

 customs of some very little known nationalities, the Inoils 

 or Esquimaux, the Apache Indians, and some of the hill 

 tribes of India. Starting with the motto that " to travel 

 over space is to travel over time," the author goes to the 

 remote regions inhabited by these tribes in order to see man 

 as one might expect him to have been in the youngest days 

 of his history. -lust as the embryologist reads something 

 of the past history of a species by an examination of the 

 phenomena the organism now presents in its earliest stages, 

 so the ethnologist tries to recover something of the history 

 of the progress of the human species by observations on 

 those esaniples of it which are now in the most elementary 

 condition. The idea is a fascinating one ; indeed, as 

 the author says, " certain customs, the meaning of 

 which has never been suspected even by those w-ho prac- 

 tise them, are in their own way as interesting as it 

 would be to an archieologist to unearth a lacustrine city, 

 or to a zoologist to discover a pterodactyl dabbling in 

 an Australian marsh"; and its interest is still further 

 enhanced by the keenness of perception which the author 



