aeontologists to learn a little more
carefully that scientific "ars artium," the art of saying "I don't know."
And to this end let us define somewhat more exactly the extent of these
pretensions of palaeontology.

Every one is aware that Professor Bronn's "Untersuchungen" and Professor
Pictet's "Traite de Paleontologie" are works of standard authority,
familiarly consulted by every working palaeontologist. It is desirable to
speak of these excellent books, and of their distinguished authors, with
the utmost respect, and in a tone as far as possible removed from carping
criticism; indeed, if they are specially 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 palaeontologists and geologists, not only on
the Continent but in this country, as expressing some of the best-
established results of palaeontology. 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 faunae and
florae 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 geological 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 temperature, which first
began to be felt at the poles.

It is not now proposed to inquire whether these doctrines are true or
false; but to direct your attention to a much simpler though very
essential preliminary question--What is their logical basis? what are the
fundamental assumptions upon which they all logically depend? and what is
the evidence on which those fundament