THE FIRST CHAPTER OF THE GEOLOGICAL RECORD. 351 
ethnology or the history of mankind, to ignore everything con- 
nected with the subject before printed records existed, or as if 
an astronomer was advised to discard all discoveries of which 
he had not tangible evidence as to their correctness. Just, 
however, as the recent advances of the collateral sciences have 
cleared up so many difficulties, and have added so much to our 
knowledge of prehistoric times, and the condition of the 
human race in earliest periods, or of parts of the cosmical 
system, which the astronomer of old could never even have 
imagined to be within man’s power of investigation ; so it is to 
be expected, with the aid of our daily improving information 
and appliances, that proportionate advances may also be made 
in our knowledge of what may be termed the prozoic history of 
the earth ; that is to say, of the different stages through which 
our globe has passed before it became fitted for the habitation 
of organisms even so low in the scale of life as are met with in 
the previously mentioned formations, which modern geologists 
appear so often to regard as the very ultima thule of their 
investigations. 
On the present occasion it is proposed to make an attempt 
to sketch out such an introductory chapter in geology as is 
here referred to, premising, however, that from its very nature 
it cannot be other than in the highest degree theoretical, and 
must be regarded only as an essay, in which the more recent 
discoveries in physical and chemical science are appealed to in 
elucidation of a subject which, without their aid, would be all 
but unapproachable ; and this is here brought forward in the 
belief that attempts made from time to time, to generalise and 
put into shape the somewhat disconnected facts and observa- 
tions relating to this subject, cannot but do good, notwith- 
standing that it must at the same time be self-evident that the 
views herein expressed will require to be modified from time 
to time, according as the progress of scientific investigation 
furnishes more reliable and extended data for generalising 
upon than are in our possession at the present moment. 
As is well known, even the most ancient philosophers enter- 
tained the opinion that our globe had not always been what it 
was in their age ; that it had passed through varied phases, 
and that it once upon a time had even had a commencement 
to its present career. Later on, when astronomy came to be 
studied as a science, astronomers went still further, and rea- 
soned from a consideration of the earth’s form, &c., that it 
must at a remote period have been in a fluid, or at least plastic 
condition ; a result which the subsequent observations on the 
temperature of the earth in depth and the products of volcanic 
action confirmed, and led to the conclusion that our globe 
must once have been a sphere of molten matter, which had 
