ANNIVERSARY ADDRESS TO THE GEOLOGICAL SOCIETY 515 
the first of all living existences; and to trace out the law of pro- 
gress from them to us. 
It may not be unproftable to bestow on these professions a some- 
what more critical examination than they have hitherto received, in 
order to ascertain how far they rest on an irrefragable basis, or 
whether, after all, it might not be well for paleontologists to learn 
a little more carefully that scientific “ars artium,” the art of saying 
“T don’t know.” And to this end let us define somewhat more 
exactly the extent of these pretensions of paleontology. 
Every one is aware that Professor Bronn’s ‘Untersuchungen’ 
and Professor Pictet’s ‘Traité de Paléontologie’ are works of stan- 
dard authority, familiarly consulted by every working paleontologist. 
It is desirable to speak of these excellent books, and of their distin- 
guished authors, with the utmost respect and in a tone as far as 
possible removed from carping criticism ; indeed, if they are spe- 
cially cited in this place, it is merely in justification of the assertion 
that the following propositions, which may be found implicitly or 
explicitly in the works in question, are regarded by the mass of 
paleontologists and geologists, not only on the Continent but in this 
country, as expressing some of the best-established results of pala- 
ontology. Thus :— 
Animals and plants began their existence together, not long after 
the commencement of the deposition of the sedimentary rocks, and 
then succeeded one another in such a manner that totally distinct 
faune and flore occupied the whole surface of the earth, one after 
the other, and during distinct epochs of time. 
A geological formation is the sum of all the strata deposited over 
the whole surface of the earth during one of these epochs: a geo- 
logical fauna or flora is the sum of all the species of animals or 
plants which occupied the whole surface of the globe during one of 
these epochs. 
The population of the earth’s surface was at first very similar in 
all parts, and only from the middle of the Tertiary epoch onwards 
began to show a distinct distribution in zones. 
The constitution of the original population, as well as the numerical 
proportions of its members, indicates a warmer and, on the whole, 
somewhat tropical climate, which remained tolerably equable 
throughout the year. The subsequent distribution of living beings 
in zones is the result of a gradual lowering of the general tempe- 
_rature, which first began to be felt at the poles. 
It is not now proposed to inquire whether these doctrines are true 
Le 
