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{Diagram}

Diagram showing successive states obtaining in ice, before, during, and after the passage of the skate.  The temperatures and pressures selected for illustration are such as might occur under ordinary conditions.  The edge of the skate is shown in magnified cross-section.

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Was not sufficient to melt the ice, the friction was much the same as that of metal on glass.  Ice is not slippery.  It is an error to say that it is.  The learned professor was very much astray when he said that you could skate on ice because it is so smooth.  The smoothness of the ice has nothing to do with the matter.  In short, owing to the action of gravity upon your body, you escape the normal resistance of solid on solid, and glide about with feet winged like the messenger of the Gods; but on water.

A second condition essential to the art of skating is also involved in the melting of the ice.  The sinking of the skate gives the skater “bite.”  This it is which enables him to urge himself forward.  So long as skates consisted of the rounded bones of animals, the skater had to use a pointed staff to propel himself.  In creating bite, the skater again unconsciously appeals to the peculiar physical properties of ice.  The pressure required for the propulsion of the skater is spread all along the length of the groove he has cut in the ice, and obliquely downwards.  The skate will not slip away laterally, for the horizontal component of the pressure is not enough to melt the ice.  He thus gets the resistance he requires.

You see what a very perfect contrivance the skate is; and what a similitude of intelligence there is in its evolution.  Blind intelligence, because it is certain the true physics of skating was never held in view by

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the makers of skates.  The evolution of the skate has been truly organic.  The skater selected the fittest skate, and hence the fit skate survived.

In a word, the possibility of skating depends on the dynamical melting of ice under pressure.  And observe the whole matter turns upon the apparently unrelated fact that the freezing of water results in a solid more bulky than the water which gives rise to it.  If ice was less bulky than the water from which it was derived, pressure would not melt it; it would be all the more solid for the pressure, as it were.  The melting point would rise instead of falling.  Most substances behave in this manner, and hence we cannot skate upon them.  Only quite a few substances expand on freezing, and it happens that their particular melting temperatures or other properties render them unsuitable to skating.  The most abundant fluid substance on the earth, and the most abundant substance of any one kind on its surface, thus possesses the ideally correct and suitable properties for the art of skating.

I have pointed out that the pressure must be such as to bring the temperature of melting below that prevailing in the ice at the time.  We have seen also, that one atmosphere lowers the melting point of ice by the 1/140 of a degree Centigrade; more exactly by 0.0075 deg..  Let us now assume that the skate is so far sunken in the ice as to bear for a length of two inches, and for a width of one-hundredth of an inch.  The skater weighs,