176 Phillips— Geological Address. 
origin above the Chalk were carelessly, if not contemptuously, classed 
as ‘superficial deposits;’ now they have acquired a large and regular 
history, embracing a great succession of organic life, in the sea and 
on the land, which is appropriately crowned by the works of intelli- 
gent man. Not long since, the ‘diluvium’ or ‘drift’ was merely an 
ill-understood basis for ill-considered speculation: now we have 
classified its parts; have begun to survey the movements of land and 
sea which preceded and accompanied these latest superficial accumu- 
lations; and have even ventured to apply to them measures of time, 
in a continuous chronology. 
The new problems opened by these researches, the inferences to 
which they lead, and the speculations which they suggest, require 
only to be named. How to explain the all but universal elaciation 
of the mountain-regions of Europe—once, or perhaps twice, since 
the era of the Crag ; how to trace the course and limits of those gelid 
waters which since that era rose to half the height of Helvellyn and 
Snowdon ; how to account for the changes of physical geography 
which allowed Hippopotami to be buried in the sediments of a York- 
shire river, troops of Mammoths to crowd the Cotswold Hills, and 
the mingled remains of Reindeer and Man to fill the caverns of the 
South of Fr ance,—these and many more questions of equal importance 
occupy the attention of geologists, and give a special interest to the 
later geological periods. 
In each of these cases, and in all which come before geologists 
for interpretation, there is one general rule :—we compare always the 
ancient phenomena with the most similar effects we can find of forces 
now in action. 
As in existing nature the amount of effect produced by known 
causes varies with the conditions of each case—as the sun’s effect 
varies from hour to hour, from day to night, from summer to winter, 
and from year to year, as the force of moving water is greater or less 
according to the slope of the ground, and the sea’s movement is 
modified by the age of the moon and the position of land—so in 
earlier nature the combinations of phenomena varied, and the 
measures of effect were modified accordingly. In another point of 
view the aspect of nature is found to be variable, and subject to 
cycles of change, periods of greater and less effect of particular forces 
which in their own nature are constant. The distance of the earth 
from the sun is not constant, the form of its orbit is not constant, it 
was not always nor will always be nearer to the sun in winter than 
in summer. From these varied conditions, which are measured by 
long astronomical periods, cycles of greater and less heating effect on 
thie: earth in general, and on parts of it in particular, arise; so that 
speculations as to the causes of the differences of climate during 
geological periods are entirely incomplete if we leave out of view 
these real and definite sources of terrestrial vicissitude. Whether 
whey are sufficient, and justly applicable to the facts established in 
geology, is a proper subject of deliberate inquiry. 
Among the facts put in evidence by geology regarding the former 
condition of the land and sea, none are so convincing of great change 
