Professor Tyndall, in speaking of the amount of energy that is given up between the points where the constituent gases unite to form nine pounds of water and the point where it congeals as ice, says: "Our nine pounds of water, at its origin and during its progress, falls down three precipices--the first fall is equivalent in energy to the descent of a ton weight down a precipice 22,320 feet high-over four miles; the second fall is equal to that of a ton down a precipice 2900 feet high, and the third is equal to a fall of a ton down a precipice 433 feet high. I have seen the wild stone avalanches of the Alps, which smoke and thunder down the declivities with a vehemence almost sufficient to stun the observer. I have also seen snowflakes descending so softly as not to hurt the fragile spangles of which they are composed. Yet to produce from aqueous vapor a quantity which a child could carry of that tender material demands an exertion of energy competent to gather up the shattered blocks of the largest stone avalanche I have ever seen and pitch them to twice the height from which they fell." When we contemplate the foregoing facts as related to so small an amount of water as nine pounds, and multiply this result by the amount of snow- and rainfall each year and the amount of ice that is congealed and again liquefied by the power of the sun's rays, we are appalled, and shrink from the task of attempting to reduce the amount of energy expended in a single year to measurable units. Having considered water in its relation to heat in the preceding chapters, we will now take up the subject of water in its relation to ice and snowfall and the phenomena exhibited in ice rivers, commonly called glaciers.