18 
travel across, and how did they get up the hill? Sometimes these 
erratics are curiously marked with parallel scratches, sometimes 
with two or three sets of them crossing each other. Similar mark- 
ings can also be seen on the rocks in situ on each side of the valley 
and in the bed of the valley. Frequently the faces of these rocks 
are polished quite smooth, as if an enormous weight had been 
slowly moving for them for long ages. You may see all these as 
you wander about in the Alps or in the Scottish Highlands; the 
valleys radiating from Snowdon abound with deeply scored masses, 
the marks as a rule all tending down the valleys. What are these 
marks? How were they made? What were the graving tools ? 
As men travelled about more and studied more deeply what they 
saw, another phenomenon was noticed, viz., the occurrence of 
numerous lakes, where the marks and sigus already noticed were 
found—long narrow lakes lying in the valleys, bordered by the 
scratched rocks, and at the lower ends of these lakes huge mounds 
of debris, composed of materials found in the valleys themselves, 
and containing pebbles and blocks of all sizes, some smooth and 
rounded, others with the hieroglyphic scratches. The presence of 
these lakes and mounds must then be taken into account in any 
explanation that may be given. We may instance such localities 
as the Highlands of Scotland, the Lake District of England, and 
especially the north of Europe and of Nort America. 
I have put before you the problem,—What have we to say in 
explanation of it ? 
It is the general practice now among all students of nature, 
geologists especially, to try to explain all phenomena by the action of 
known causes. In the early part of the century it was not so, and 
the phenomena I have so briefly described, so extensive in their 
results and betokening apparently such huge and unfamiliar 
agency, seemed above all others incapable of explanation in such 
fashion—all spoke of irregularity and confusion. And so men fell 
back on hypotheses, on invented, not discovered, explanations, as 
man is soprone todo. There is no harm in the thing itself, so long 
as you have sufficient ground to go upon, but to invent out of one’s 
inner consciousness a wild baseless explanation is not scientific, 
though it may sometimes be easy—easier than searching for facts. 
A friend of mine, who is always trying to explain the unexplainable, 
whenever he is non-plussed, says 1t must be electricity, of which 
agent he has invented several varieties unknown to the scientific 
world, just as in medieval times all mysteries were referred to the 
agency of the great magi¢ian, Michael Scott, 
A wizard of such dreaded fame, 
That when, in Salamanca’s cave, 
Him listed his magic wand to wave, 
The bells would ring in Notre;Dame? 
