Ciiap. TL] 
COURSE OF THE SAP. 
49 
and to fill these holes with water in a frost. 
Here “ weak water ” splits the hardest sub¬ 
stance by turgescence, or swelling, without a 
star on its frozen column. This plan was 
changed to plugging the holes with dry wood, 
and wetting these plugs simultaneously. Here, 
again, the mysterious and marvellous power of 
turgescence performs its Herculean task with 
apparently very weak implements. A spoonful 
of water and a small bolt of wood form the 
blood and frame of a giant who, give him finger¬ 
hold, makes a joke of Milo. He changes his 
name sometimes, though. When he acts on ice, 
I should have called him dilatation. When he 
acts by heat, his name is expansion. And to 
him is confided the growth of geological vege¬ 
tation. His endogens are the Alps, the Hima¬ 
laya, and the Andes; his exogens, Vesuvius, 
Etna, and Madeira. Who shall guess from what 
depths within the earth these last receive their 
red-hot sap ? But even to raise it, after leaving 
the earth, through the pressure of the Atlantic, 
perhaps some 30,000 feet, is not a bad squirt. 
We have then, in the roots and stem, wood and 
moisture, the implements of turgescence, — a 
force unlimited in power. How to describe the 
steps by which it is to raise the sap a hundred 
E 
