PRESIDENTIAL ADDRESS. sf 
bers still contain a large amount of their origmal heat. And 
if the Solar System had a beginning, so, also, must each star 
in the heavens have had a beginning ; for the very fact that 
we can see them is a proof that they are radiating out 
energy. And, it was asked, why should not the whole /Uni- 
verse, visible and invisible, have had a common origin and 
a common beginning in time? This had been the opinion 
of Immanuel Kant in the middle of the eighteenth century, 
and, although modern astronomy has not altogether con- 
firmed his speculations, it has proposed a hypothesis which 
is not very dissimilar. This is the ‘“‘ Meteoritic Hypothesis,” 
and is chiefly the work of Sir Norman Lockyer and Professor 
G. H. Darwin. I will give you a short sketch of the views 
held by the former.* 
InorGanic Evouution. 
The close connection between the orbits of comets and 
those of meteoritic streams has led to the universally-ad- 
mitted conclusion that comets are neither more nor less than 
swarms of meteorites. Again, the resemblance between the 
spectra of comets and those of nebulw suggests that these, 
also, are swarms, or aggregations, of meteorites. And we 
naturally infer that the stars with similar bright-line spectra 
must be collections of meteorites. From bright-line stars 
we pass to those whose meteoritic origin is no longer to be re- 
cognised, all having blended together. Further, it is claimed 
that, by supposing variable and temporary stars to be due to 
the meeting and entanglement of two meteoritic swarms, we 
get a better explanation of the observed phenomena than 
any other hypothesis can give. 
This meteoritic hypothesis supposes that the present 
material Universe was at one time in a state of “ cosmic 
dust,”’ spread irregularly through space, and moving slowly 
in many directions. It is the original irregular distribution 
of the cosmic dust and its irregular movements which are 
the source of all the energy in the Universe. We have 
specimens of this cosmic dust in the chondroi, or spherules, 
of which many of the stony meteorites are built up. They 
are small round bodies of crystallised minerals, varying from 
microscopic dimensions to the size of a marble. Of course, 
these chondroi are not the first form in which matter existed. 
‘They are evidently due to chemical reactions, and we could 
frame several different hypotheses as to their origin and his- 
*See ‘The Meteoritic Hypothesis,” Macmillan, 1890; and ‘ Inorganic 
Eyolution,’? Macmillan, 1900. 
