The other Method of Scating, which is known in England by the Name of Rolling, is done upon the same Principle as the former, only as you have no Occasion for Expedition, you have an Opportunity of
dweling longer upon your Strokes, and your Time; by which Means, instead of describing a small Curve, you describe a large one.
It will be necessary to explain the Cause of this Motion, before we can make the Reader sensible of what we intend to say.
All Bodies that are put into Motion upon the Surface of the Earth, are acted upon by two Forces; namely, a Projectile Force and a Centripetal Force. The Projectile Force is that which is given it by the Hand or Strength of any Person, and the Centripetal Force is that which causes all Bodies to seek the Center of the Earth. For Instance, when a Stone is cast into the Air to any Distance, the Reason why it does not move on to Eternity without stopping (as it ought to do by the Principles of Mechanics) is, because the Centripetal Force keeps continually acting upon it, till it has pulled it down to the Ground again: This serves to explain what is meant by a Centripetal Force.
Now, when a Person scates, he is acted upon by these two Forces, as other Bodies in Motion are. It is the Projectile Force which throws him upon the Outside of the Scate, till he has got quite out of the Center of Gravity, by which Means he would be pulled to the Ground by the Centripetal Force, if he was not supported by the Projectile Force, which is strong enough to make Head against the Centripetal for a little while (in the same Manner as it is able to keep a Stone in the Air till it is spent) and by that Time the Person scating has recovered himself into an erect Posture. This Projectile Force is given by a Stroke of the Foot, inclined to the Plain of the Ice; by which Means, the whole Edge of the Scate takes hold, and is your moving Force; and the more of the Edge of the Scate a Person uses in his Stroke, the easier he will go to himself, and the greater Velocity he will move with: For if he dwells more upon the Heel of the Scate than the Toe, or vice versâ, he not only loses Part of his moving Force, by
losing Part of the Edge of his Scate, which is absolutely the moving Force, but he likewise encreases his Friction, which ought to be destroyed as much as possible; and at the same Time loses that Symmetry of Gesture, upon which the Gracefulness of his Attitude depends.
When a Person scates properly, he keeps the Foot that he strikes with in such a Posture upon the Ice, as to make the whole Scate take hold of it sideways, without destroying his progressive Motion; and instead of kicking up his Heel behind, just when he takes Leave of the Ice, with the Foot which has been striking, he gives his Toe a Turn outwards, which not only gives him a genteel Air, being according to the Rules of Dancing, but likewise sends him with twice the Force upon the Outside, as it adds to that Projectile Force which is to make Head against the Centripetal, and to keep him upon his Legs after he has got out of the Center of Gravity; and which uncommon Phœnomenon gives that Surprize and Pleasure to a
Beholder, which he perceives at the Sight of a fine Scater.
I mention this, because I have met with those who have obstinately persisted in it, that some Persons who kick up their Heels behind, and strike only with the Toe of their Scate, because they can go a Snail's Gallop upon the Outside, are fine Scaters; when they are making Use of a Method which is repugnant to the very Principles of Mechanics.