e solar
star is a weightier body than the average Sirian star.[1382]

On November 17, 1887, Sir Norman Lockyer communicated to the Royal
Society the first of a series of papers embodying his "Meteoritic
Hypothesis" of cosmical constitution, stated and supported more at large
in a separate work bearing that name, published in 1890. The fundamental
proposition wrought out in it was that "all self-luminous bodies in the
celestial space are composed either of swarms of meteorites or of masses
of meteoric vapour produced by heat."[1383] On the basis of this
supposed community of origin, sidereal objects were distributed in seven
groups along a temperature-curve ascending from nebulae and gaseous, or
bright-line stars, through red stars of the third type, and a younger
division of solar stars, to the high Sirian level; then descending
through the more strictly solar stars to red stars of the fourth type
("carbon-stars"), below which lay only the _caput mortuum_ entitled
Group vii. The ground-work of this classification was, however,
insecure, and has given way. Certain spectroscopic coincidences,
avowedly only approximate, suggesting that stars and nebulae of every
species might be formed out of variously aggregated meteorites, failed
of verification by exact inquiry. And spectroscopic coincidences admit
of no compromise. Those that are merely approximate are, as a rule,
unmeaning.

In his Presidential Address at the Cardiff Meeting of the British
Association in 1891, Dr. Huggins adhered in the main to the line of
advance traced by Vogel. The inconspicuousness of metallic lines in the
spectra of the white stars he attributed, not to the paucity, but to the
high temperature of the vapours producing them, and the consequent
deficiency of contrast between their absorption-rays and the continuous
light of the photospheric background. "Such a state of things would more
probably," in his opinion, "be found in conditions anterior to the solar
stage," while "a considerable cooling of the sun would probably give
rise to banded spectra due to compounds." He adverted also to the
influential effects upon stellar types of varying surface gravity, which
being a function of both mass and bulk necessarily gains strength with
wasting heat and consequent shrinkage. The same leading ideas were more
fully worked out in "An Atlas of Representative Stellar Spectra,"
published by Sir William and Lady Huggins in 1899. They were, moreover,
splendid