666 Ph yystography. [ October, 
more comprehensive survey of that philosophy, whose aim it is 
to comprehend and consolidate the widest generalization of 
science. 
A rude attempt at such a survey of the principles of geology 
and the bordering branches of science will be found in the follow- 
ing pages. They are from the notes of a lecture which formed the 
last of a course delivered before a school audience. In that lec- 
ture I did my best to give a rough sketch of that chain of events by 
the study of which we may build up a history of the Earth, while I 
endeavored at the same time to lead my hearers upwards from the 
simple to the complex ; for I hold that the teacher of science should 
lead his pupils from the well known, through the less known, to 
the unknown. Taking a few simple and obvious facts as a basis, 
he should first test whether those whom he teaches really know 
them to be facts, and then, carefully building upwards, seeing 
that each stone of his superstructure rests securely on one which 
has before been firmly laid down in its true place, he should mount 
slowly and surely, until, at last, he reaches that rare atmosphere 
of the unknown in which, for the present at least, no man may 
build. 
Standing by the sea-side, then, let us inquire of Nature con- 
cerning the things which we see around us. The waves roll in 
upon the shore, the wind blows freshly in our faces, a heavy 
storm-cloud hangs over the distant horizon, at our feet is a little 
streamlet running over the sands to the sea; behind us is the 
white chalk cliff, capped with sand and clay. 
How come these waves, and what are they doing? shall be 
our first question. The answer to the first part of the question is 
so obvious that a child will not hesitate to reply, that it is the 
wind which produces the waves. At first a mere cat’s paw on the 
surface of the sea, the growing ripples are, as the wind continues, 
hurried onwards, increasing both in length and breadth, and, 
where the water is deep, in velocity of motion, until they become 
the great waves, some fourteen feet high from trough to crest, which 
we see on our coast during a storm, and finally, if they have a 
fair field, develop into ocean billows, twenty-six feet high in the 
: a ‘Atlantic, forty feet high in the Southern Ocean. In the open sea 
_ the water is not carried forward by this wave motion. We may 
watch the sea-bird rise and fall as the wave passes under her. 
idole not e SN on its summit. But when the wave | 
