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England used to amuse themselves by fastening the bones of an animal beneath their feet, and pushing themselves about on the ice by means of a stick pointed with iron.  With such skates, any performance either on inside or outside edge was impossible.  We are a conservative people.  This exhilarating amusement appears to have served the people of England for three centuries.  Not till 1660 were wooden skates shod with iron introduced from the Netherlands.  It is certain that skating was a fashionable amusement in Pepys’ time.  He writes in 1662 to the effect:  “It being a great frost, did see people sliding with their skates, which is a very pretty art.”  It is remarkable that it was the German poet Klopstock who made skating fashionable in Germany.  Until his time, the art was considered a pastime, only fit for very young or silly people.

I wish now to dwell upon that beautiful contrivance the modern skate.  It is a remarkable example of how an appliance can develop towards perfection in the absence of a really intelligent understanding of the principles underlying its development.  For what are the principles underlying the proper construction of the skate?  After what I have said, I think you will readily understand.  The object is to produce such a pressure under the blade that the ice will melt.  We wish to establish such a pressure under the skate that even on a day when the ice is below zero, its melting

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point is so reduced just under the edge of the skate that the ice turns to water.

It is this melting of the ice under the skate which secures the condition essential to skating.  In the first place, the skate no longer rests on a solid.  It rests on a liquid.  You are aware how in cases where we want to reduce friction—­say at the bearing of a wheel or under a pivot—­we introduce a liquid.  Look at the bearings of a steam engine.  A continuous stream of oil is fed in to interpose itself between the solid surfaces.  I need not illustrate so well-known a principle by experiment.  Solid friction disappears when the liquid intervenes.  In its place we substitute the lesser difficulty of shearing one layer of the liquid over the other; and if we keep up the supply of oil the work required to do this is not very different, no matter how great we make the pressure upon the bearings.  Compared with the resistance of solid friction, the resistance of fluid friction is trifling.  Here under the skate the lubrication is perhaps the most perfect which it is possible to conceive.  J. Mueller has determined the coefficient by towing a skater holding on by a spring balance.  The coefficient is between 0.016 and 0.032.  In other words, the skater would run down an incline so little as 1 or 2 degrees; an inclination not perceivable by the eye.  Now observe that the larger of these coefficients is almost exactly the same as that which Perry found in the case of well-greased surfaces.  But evidently no