( 5 ) 
grosses very slowly, the two rock masses stick for a time and 
then slip suddenly, the result is an earthquake more or less vio¬ 
lent according to the rate of movement and the time it has been 
interrupted. A slip of only a few inches may produce disaster- 
ous results to the inhabitants of a country while modifying the 
configuration but little. In the course of this sketch I shall have 
occasion to refer to enormous changes in configuration, some of 
which have taken place with great violence. 
It is impossible to discuss history without some system of chro¬ 
nology. That which is counted by years and days is the simplest 
but not always the most convenient. We divide our years into 
months which are periods of different lengths and which receive 
arbitrary names. In some countries still more irregular divisions 
are adopted for certain purposes. Thus in England a law is 
referred to by the year of the reign of the sovereign in which it 
was passed. In geology we cannot use divisions by years, for 
we have no means of ascertaining the precise lapse of time be¬ 
tween events. Geological history is divided and subdivided into 
periods marked by the character of the animals and plants which 
flourished. This division is not absolutely sharp, but no better 
method has been devised. I shall here employ only the largest 
divisions of geological time compatible with the discussion in 
view. 
The lowest rocks known to contain organic remains is called 
the Palaeozoic, but underlying this group is an enormous thick¬ 
ness of rocks, similar to those occurring along the shore of 
Newport, in which no organic remains have been detected with 
certainty and which is known as the Archaean. The Archaean 
rocks have been subjected to violent movements and the action of 
heated waters, and it is highly probable that any fossils they 
might have contained would have been obliterated. Modern 
naturalists are practically a unit in accepting the Darwinian 
theory of development. If this theory is correct, there must have 
been life long before the Palaeozoic, for the earliest known fossils, 
though not representing the most advanced types, are far in ad¬ 
vance of the lowest forms of life. The Archaean is very widely 
spread on the Pacific slope and probably underlies the entire 
area. This means of course that, at one time or another during 
