TRANSAGTIONS OF SECTION A. 707 — 
“The following Report and Papers were read :— 
1. Report on the Establishment of a National Physical Laboratory. 
a. «See Reports, p. 82. 
4. On the Evolution of Stellar Systems. By Isaac Roserts, D.Sc., LBS. 
The evidence of stellar evolution which it is now proposed to submit may be 
presented in either of two forms :—(1) By tracing back from the visually finished 
stars to the material of which: they may have been built up; this we may term 
the analytical method. (2) By tracing their development from an amorphous 
material to the visually finished stars ; this would be the synthetical method. The 
first of these will now be considered. 
Tt should be noted that the evidence has been obtained by processes which are 
not subject to the disturbing influence of human or personal imperfections. 
A series of photographs, untouched by handwork, were shown, and the objects 
as they undoubtedly exist in the sky were thus submitted to judgment. 
A small selection of characteristic photographs were exhibited by lantern 
projections on a screen. ; 
The first was a photograph: of the sky in the constellation Auriga, which was 
taken with an exposure of the plate during 90 minutes, and attention was drawn 
to the remarkable groups, curves, and lines of stars which were clearly shown 
upon it. Some of them are constituted of bright stars of nearly equal magnitude ; 
some are of faint stars, also of nearly equal magnitude ; some are of both bright 
and faint stars, and there is much regularity in the spacing distance between the 
stars in the several groups. These appearances are persistently found upon all 
photographs, taken with a long exposure, in any part of the sky where the stars 
are numerous. 
In order to emphasise these statements, two photographs of stars in the con- 
stellation Argo and one in Cassiopeia were shown on the screen, and upon them 
also was seen the appearances referred to; and hundreds of photographs of other 
regions of the sky could be shown in further confirmation of these features. 
The explanation offered to account for the grouping of the stars, that they were 
so placed from the beginning, is not the only one. Photographs were then shown 
which suggest, if they do not demonstrate, stellar evolution. 
The spiral nebula in Pisces clearly shows that the spirals consist of nebulous 
matter with faint stars immersed in it, and of bright stars apparently in their 
completed forms. The curvatures and the general arrangements of these stars, 
both bright and faint, can be readily matched with similar curves seen on the 
photographs already shown; but the taint stars which are immersed in the nebu- 
losity are not yet in the completed form, and will not arrive at that stage until 
the whole of the nebulosity has been absorbed, when they will stand out clearly 
separated like the other stars. 
The spiral nebula in the constellation Ursa Major, like the last, has spirals 
formed of nebulous matter, with numerous starlike condensations in it; and six 
well-defined stars are involved at irregular intervals. The nebulous condensations 
are not so regular in their outlines as are those on the first photograph, and are 
suggestive of a more recent period in their development. 
The spiral nebula in Ursa Major, like the two others, consists of faint starlike 
condensations immersed in the convolutions. [here are also five well-formed 
stars involved, but the stellar condensations are less fully developed in this nebula. 
The fourth photograph was of the spiral nebula in Canes Venatici, and it was 
observed that the conyolutions are more strongly shown in this than in the other 
nebule ; also that they consist of several well-formed stars, whilst the star-like 
condensations show various degrees of development, from the likeness of a nebulous 
star to that of diffused nebulosity. 
The fifth photograph, the spiral nebula in 7’rzangulum, shows the spirals to be 
crowded with stars and star-like condensations in the midst of diffused nebulosity. 
