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artificial system of lubrication could hope to equal that which exists between the skate and the ice.  For the lubrication here is, as it were, automatic.  In the machine if the lubricant gets squeezed out there instantly ensues solid friction.  Under the skate this cannot happen for the squeezing out of the lubricant is instantly followed by the formation of another film of water.  The conditions of pressure which may lead to solid friction in the machine here automatically call the lubricant into existence.

Just under the edge of the skate the pressure is enormous.  Consider that the whole weight of the skater is born upon a mere knife edge.  The skater alternately throws his whole weight upon the edge of each skate.  But not only is the weight thus concentrated upon one edge, further concentration is secured in the best skates by making the skate hollow-ground, i.e. increasing the keenness of the edge by making it less than a right angle.  Still greater pressure is obtained by diminishing the length of that part of the blade which is in contact with the ice.  This is done by putting curvature on the blade or making it what is called “hog-backed.”  You see that everything is done to diminish the area in contact with the ice, and thus to increase the pressure.  The result is a very great compression of the ice beneath the edge of the skate.  Even in the very coldest weather melting must take place to some extent.

As we observed before, the melting is instantaneous,

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Heat has not to travel from one point of the ice to another; immediately the pressure comes on the ice it turns to water.  It takes the requisite heat from itself in order that the change of state may be accomplished.  So soon as the skate passes on, the water resumes the solid state.  It is probable that there is an instantaneous escape, and re-freezing of some of the water from beneath the skate, the skate instantly taking a fresh bearing and melting more ice.  The temperature of the water escaping from beneath the skate, or left behind by it, immediately becomes what it was before the skate pressed upon it.

Thus, a most wonderful and complex series of molecular events takes place beneath the skate.  Swift as it passes, the whole sequence of events which James Thomson predicted has to take place beneath the blade Compression; lowering of the melting point below the temperature of the surrounding ice; melting; absorption of heat; and cooling to the new melting point, i.e. to that proper to the pressure beneath the blade.  The skate now passes on.  Then follow:  Relief of pressure; re-solidification of the water; restoration of the borrowed heat from the congealing water and reversion of the ice to the original temperature.

If we reflect for a moment on all this, we see that we do not skate on ice but on water.  We could not skate on ice any more than we could skate on glass.  We saw that with light weights and when the pressure