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History of Curling
Chapter II. The science of curling


HAT is the Science of Curling? The question was put to us by a practical curler when he saw the heading of this chapter, and we were not surprised when he added that he had never heard of such a thing before. We are not responsible for the title. "The Science of Curling-stones" might perhaps be a better one. But we are quite prepared to defend it as it stands, and our readers, we are sure, will see the propriety of keeping the subject separate from the "Art of Curling," which falls to be treated in our next chapter. In former times curlers generally took the material that lay nearest them, and nearly every district of Scotland has at some time or other furnished curling-stones. Now, when machinery has been introduced for their manufacture, and the facilities of railway carriage are so great, it is important to know where suitable material for curling-stones can be found. In order to decide among the varieties of stone found in different districts, it is necessary to have some fixed standard or test by which to try the different varieties. This is difficult to get. In Canada, where the ice is keen the prime requisite is a stone that is not liable to break under the excessive frost. This makes Ailsa popular there. At home we have very often to play on dull ice, and this makes Ailsa popular here. But Ailsa is too big for its weight when a Canadian wants to do the port shot in his point game, and in keen ice at home it is too keen. Burnocks, Crawfordjohns, and Plantrres are neither too keen on keen ice nor too dull on dull ice, and for these reasons they rank before Ailsas as true stones. Now, whatever our test may be, when we come to decide among varieties of stone, it is apparent that the science or exact knowledge of their composition and nature must be useful. This is why we have made a "new departure," and called in the assistance of an expert to throw light on the subject. In the coloured plate which accompanies this chapter we have given illustrations of the six kinds of stone most popular at the present day. These six varieties will be found, we believe, to cover two-thirds of the curling-stones now in use, the other third embracing such stones as are found at Carsphairn, Tinkernhill, Blantyre, &c. They have all been submitted to Professor Forster Heddle, who, as one specially fitted to do so, has been asked to explain their composition and to pronounce on their respective merits. The learned Professor's statement we now give in extenso:—

THE SCIENCE OF CURLING.

The writer, as a physicist and a petrologist, has been requested to say something upon curling, the request being formulated as follows:-

"Give a description of the varieties of stone used—such as curlers of intelligence could appreciate.

"What is the best kind of stone for the purpose?

"Supply, if possible, some information which may be made practical and useful."

This is, in a word, to speak to the science of curling—if it has any--in contradistinction to the art and to skill; to act as the guide to the inexperienced; to explain the causes of successful experience; to deal with the pabulum, and not with the performance.

The writer is not a curler. He occupies, therefore, the "coigne of vantage" of the elevated onlooker who perceives every failure, and many of their causes; though he may never be able fully to appreciate that wondrous copartnery of eye and brain and muscle, in rapidly sequential unison, guaging, decreeing, and executing that marvellous shot which elicits an applause which frequently is nothing short of ferocious.

The earliest historian of curling states that the stones employed are made from blocks of whinstone, or granite.

If this last were so, then there is no science connected with it.

But it is not so. Of ten stones in the writer's hands, and some five others named to him as in use, not one is granite. That granite could not hold its own is shewn in the following extract from a letter of an old curler:-

"I spent a winter in Aberdeen in 1846-47  got a club started, and about twenty pairs of stones from the Ayrshire quarter; but some of the club did not like the idea, and supplied themselves with Aberdeen granite ones, at a much greater cost; but they were found useless, as they could not be sent up the length of the rink. I have often wondered what could be the cause of this. I don't think it could be porosity but, possibly from interstitial matter between the crystals, the polished bottom might not be so compact but that the edges of the crystals might act as scrapers sufficiently to retard the stone. whether that be the reason or not, the fact was that they were a failure at that tine."

The shewing how stones of granite are contra-indicated, and for reasons apart from those shrewdly speculated upon by my correspondent, will form the text of my remarks upon the science of curling.

In two ways can the stones be made to shoot round a corner, to circumvent a guard.

First, by an out-elbow or in-elbow screw. Second, by inwicking. Without these it may be said there would be no game. In no way can a side bias be given to a sliding object which is left at any moment free to change its sides.

By the screw or spin one side of the stone—the inner—is ever to some extent receding from and diminishing the medial amount of friction upon the ice; while the other—the outer—is ever, to a corresponding extent, increasing that amount. The stone yields to this doubled difference, and curves away from the side of greatest resistance. Again, when the narrow sole is used, there must be some amount of lift away from the side of greatest resistance, and so will the lean to the inner side bring direct gravitation into play.

In wicking the elasticity of both stones is depended upon; and no amount of experience and skill could compensate for an ever-varying quantity, if that variation exceeded certain limits. Still less could it do so if the amount of elasticity varied at different sides of the same stone, for here experience of one side would entail error as regards the other.

As different kinds of stone have different elasticities, theoretically, and to perfect the game, a single kind should be adopted; but, as different weights of stone are permitted, and as the force of the impact is divided between striking and struck stone (in amount, of course, always depending upon the angle of striking), and as a stone will recoil further off a heavy stone than off a lighter one, there can be no hope of this theoretical perfection until men become of one strength as well as of a single mind in the matter.
By far the greater number of the rocks used as "stones" are melanges of minute crystals of different substances, interlocked in more or less confused arrangement with one another.

If this arrangement is absolutely confused and promiscuous, that may be called perfection of structure in a stone. Any diversity in this respect—any evident special structure in any part of a stone—anything that makes it "bonny," unless it is equally bonny all over, is a step in the direction of the imperfection of inequality.

It is a prettier thing to see a stone with an ugly face sitting right over the tee, than a stone lately handed round a railway carriage as "a new one, and a beauty," lying an inglorious outsider.

The point is that stones are built up of myriads of crystals, which should lie, as regards their position to each other, in all direction and why?

A crystal is a structure which is made up of little bricks, as it were, which are termed molecules. These, in being arranged in a crystal, are not allowed to go indiscriminately in any position, or in equal numbers to this side or to that. They are as much subject to positional law as are the bricks or integers in a regiment, which are not allowed to take position indiscriminately, but have appointed positions : major here, captain there, sergeant in this place, corporal in that:- [Except the general, who, it is generally believed, is allowed to go to the rear; but this may be a civilian error. Perhaps, however, it proves that he is not "a brick" at all]

This arrangement is one of design—to resist impact, and throw back the impacter. If assaulted upon flank, the regiment cannot do this well ; if upon rear, it has to face about.

So is it with a crystal. Its power of resisting impact, of repelling the impacter—its elasticity, in fact—is much greater when it presents its forefront than at the sides—nearly as 4 to 3.

Granite is made up in largest amount of a crystal substance called felspar or orthoclase. This name expresses that it splits in two directions, which lie at right angles to one another; and in most granites, although there is a general appearance of confused arrangement of ingredients, there is a dominant polar arrangement of this grain ingredient. This exists to so marked an extent that not only is the quarry foreman guided by his knowledge thereof in the disposal of his blasts, but every causeway block-dresser cleaee.4 the stone by blow and cross blow, leaving only one direction in the shaping to be chipped into the necessary form.

From this dominant polar position of a material which possesses an elasticity greater in one direction titan in all others, it results that curling-stones made of granite, while they would only travel 6 feet after an inwick on one side, would travel 8 feet if they were hit upon another ; while if both stones were of granite the 8 might become 10. Uncertainty is introduced all round ; and it is just in delicate play that the difference would make all the difference.

Aside altogether of sluggishness of the stone, as noticed in the above letter, granite is clearly unfitted as a material to be used in curling, as are all stones which, by any very distinct uniformity in the directions in which they split, indicate a uniformity in the position of the crystals which go to build them up.

This is one of the reasons why boulders are superior to the rock mass from which they apparently were derived. -Many- of these had existed as kernels or concretionary segregations in the mass of the parent rock, and, from having somewhat of a concentric arrangement of parts, they have not the tendency to definite lines. of fracture which many of these rocks exhibit (though none to the extent seen in granite).

Next to uniformity in. elasticity in staines, stands their being "true" in all states of the ice.

Without assuming to have arrived at all the causes of slugishness of stones on "drug" ice, the writer would say that he is not prepared to assign it to plates of mica, or of any ingredient projecting above the


Red Hone Ailsa

surface of the stone, and so acting as scrapers; but to certain of the ingredients crumbling away and leaving depressions, each of which becomes a lodgment for water or slosh.

It is well known that friction between surfaces differing in nature is much less than between two surfaces of the same metal or nature. In the last case cohesion is always attempting to establish a reunion, and frequently succeeds.

The natural state of matters, is the friction between the dry- stone and dry ice ; in the "drug" it is between the wet stone and wet ice in other words, between water and water. The little particles of water, lodging in the minute depressions or roughnesses in the sole of the stone, unite with the water on the surface of the ice, and the drop or drops so formed are being constantly torn through, only to reform immediately and be again ruptured. As the cohesion of water is considerable, the travelling energy of the stone is soon exhausted.

It may appear that in a highly polished stone there are no depressions for such lodgment; but there are linear pores, and where such exist there is in damp weather an instantaneous absorption of water. I find notes of this on six rocks, in some old experiments of my own. I give as extremes:-

The dolerite rock from:-

Considering that this is little more than a surface action, the difference is very great. Moreover, the Ratho rock accomplishes the absorption in one-fiftieth part of the time taken by the others. As well curl with a sponge as with Ratho. (N.B.—Granites are very bad in this respect.)

The various stones which I have examined in thin section in the microscope, to be able to speak to their composition and structure as bearing upon their suitability for curling purposes, and their relative value therefor, are:—

Excepting the first three, which are varieties of the same, all are rocks differing in components, and more or less in properties from one another.

The mineral substances which go to form them are: quartz—which confers (relative to the others) hardness, brittleness, and lightness common felspar—somewhat brittle, light, and with a tendency to rot; plagioclase felspar—less brittle, more weight; augite—heavy, sometimes brittle ; olivine—hard, heavy, tough; hornblende—heavy, when fibrous very tough; magnetic iron—very heavy, hard, brittle; micas (rarely)—soft, brittle.

The excellence of any one rock depends upon the relative amount of the hard, heavy, and tough ingredients; upon their relative firm adhesion one to the other, through a promiscuous interlocking of the component crystals; and to uniformity in structure throughout. Ceteris paribus, the smaller the grain the better.

It is upon the above lines, and especially upon the structure as disclosed by the microscope, that relative values are assigned below.

AILSAS.—Of the above stones, the first three are variations of a rock which is the plug to the throat of a volcano of geologically recent times—a volcano which apparently had done no more than form a throat and then plug it. The rock would at present bear the general term of granophyre. From its containing a blue-green mineral, not yet found in the usual varieties, it has been termed Ailsite distinctively. It contains much quartz, much felspar—both, structurally and chemically, in a bad condition; the green mineral is not uniformly distributed, but is in patches; there are not infrequent small holes in the rock, and its-whole structure is confused and `'messy." The Red Alils is in a state of incipient rotting, its felspar is kaolinised and greasy, and stained with iron oxide.

On account of the large amount of quartz, the stone must be light and hard; from its general uniformity not liable to flaws, but it is a uniformity in a poor, if not in a bad direction.

From most of the above defects the Blue hone is, however, free. It is a stone of remarkable uniformity of structure and fineness and closeness of grain. No cavities are to be seen, and although there is much the same superabundance of quartz, and want of precision in the development of its crystals, it is a stone of marked excellence.

CARSPHAIRN.—This is a stone the first inspection of which is not in its favour, but which increases in apparent excellence the more it is examined. The rock is a quartz porphyry, and that which is unpromising is the large amount of quartz, bringing in lightness and brittleness; and, secondly, that it is a porphyry, which, in a certain sense, implies absence of uniformity.

A porphyry has a structure in which crystals are embedded in a paste, in the same manner as raisins are embedded in a dumpling. Here is absence of uniformity. As the raisins may be picked out of the dumpling, so might the crystals be knocked out of the. paste ; and though it might be held that the raisins were the best part of the dumpling, yet it is not so if the "raisins" bring in lightness and brittleness, and if their removal left a number of holes.

An examination of sections of the rock, however, skews that the surfaces of the quartz crystals are rough, enabling the paste firmly to grip them ; and as that paste is itself of remarkable uniformity—as is the general structure of the stone, there being an absolute freedom from holes—this stone, apart from its lightness, probably is one of great excellence. Never having seen it in mass, I cannot speak to freedom from flaws.

CRAWFORDJOHN.—Another porphyry, but here a porphyritic dolerite. Dolerite is our present name for what used to be called "greenstone." They consist of augite, plagioclase, felspar, magnetite; and sometimes, and all the better for curling-stones, of olivine. In a paste or magma of the former of these, pen sized crystals of augite are impacted —fortunately in every position.

For reasons above given, the structure of this rock would not be in its favour, were it not that here also the surfaces of the embedded crystals are rough and the cryrstals lie all in one direction. The rock would. split somewhat easily in a certain direction. From the general compactness of this rock, and its freedom from vacunities, should be an excellent one; while its components confer upon it surpassing weight.

BURNOCK WATER. - Another dolerite, but contains no embedded crystals. It has much olivine and finely sprinkled magnetite, with an

exceedingly fine, sharply interlocked, and well-developed crystalline structure of marvellous uniformity. The olivine gives increased weight, hardness, and toughness ; and this, taken along with its structure, places it markedly the best of all the stones.

TINKERHILL.—This consists of a rock of much the same structure as dolerite, but it contains Hornblende and not augite, and is termed diorite. This special diorite has the hornblende passing into epidote. It is a good rock, but not so good as dolerite. It seems porous.

CRIEFF, common. — A very strange rock. Being got solely from boulders scattered over a considerable range of country, it varies a good deal in character, though all may be called hornblende rock. The large size of the crystals of hornblende which it contains, and their flakey nature, are far from promising. Still, when polished, they "come up" wonderfully close and compact in appearance. Epidote, which is seen in yellow patches, and a massive granular felspar, are the chief other ingredients. From the distinct foliacious appearance of the hornblende, I should be suspicious of this rock with water on the ice.

CRIEFF, black.—This, found on the south, instead of the north side of the Earn, is a hornblende schist, formed of minute sparkling scales of hornblende, with small kernels of quartz.

It is very uniform and fine grained, excessively tough, and hard to break ; will be almost black when polished. It also stands with a slight mark of doubt as regards water ; but otherwise excellent.

CRIEFF SERPENTINE.--At first sight a strange rock to make use of in a game of "dunts," for most serpentine is soft. Some varieties, however, approach in hardness to the diorites; and for closeness none of the others can approach them; their oily polish, also, should make them impervious to water.

In adjudicating relative total merits, I would put them

That is, supposing thoroughly good examples are got of each, and not quarried, and, still less, blasted stones.

Gunpowder expands in being fired in every direction; and though the block may have rent in only two or three, it may have been strained, though invisibly, in others; and after a succession of whacks, upon the point opposite to the entrance line of such strain, the strain becomes a fracture.

Boulders have, when well rounded, come through a long experience of grinding against each other, and against mother earth, under the pressure of enormous masses of ice; or, if angular, of rolling down cliffs, to lie upon the surface of the ice, and to be air-wasted, so that every rent would be found out and delineated on the surface.

This brings the writer to useful hints.

1st. Give twice the price for a boulder of any of the first five rocks in above list that you would for the finest-looking pair of stones of any not known to be boulders.

2nd. If you cannot get a boulder, search the foundations of the dykes. Whole boulders, or portions large enough, are there stored away.

3rd. In purchasing stones, reflect the light from the polished soles; and if you see any small holes, roughnesses, or lines of any kind, have nothing to do with them.

4th. Suggestion.—Get the stones gently heated up, for, say, a day (if previously "dry"), above the temperature of warm water (not before the tire), and thou soak them for twenty-four hours in "finish" (a solution of 3 oz. of shellac to the gallon of methylated spirit). Rub them dry after dripping them, and set them iu a warm place for other twenty-four hours. This will prevent water soaking into them.

5th. For the collective advantage of curlers.—flare "stones," 3 inches in diameter, made of all stones used, or proposed to be used—shape and polish to be perfect. Have a billiard-table, or dead•flat table, cloth-covered. Have a circle, size of width of the table, graduated in angles, printed upon the cloth, with central tee, and also with a number of gradually diminishing circles. have one test stone, of same size as others, suspended by cord or wire, of 8 or 10 feet in length, fair above the tee, and so as barely to touch the cloth. Draw back the test-stone in straight line one or more feet from the tee, and tie it back by thread. Place the various stones, successively, upon the tee, and set, fire to the retaining thread. The relative amount of recoil or elasticity of the various kinds of stone will so be ascertained. Accurately replace the tee-stone, and draw back the test-stone, in succession to the different angles marked upon the home-half of the circles, allowing it to strike successively at different angles. So may be ascertained:

1. How far the angle of impact departs from the angle of take-off.
2. If the angle of recoil of the struck ball, as in inwicking, is the same as the angle of deflection of the striking ball.
3. What is the relative amount of travel of the striking and struck balls—relatively to the angle at which they are struck?

The player who carries such knowledge in his head will have a great advantage over the man who plays by hand and eye alone.

6th. Let pieces of each kind of stone, about a cubic inch in size., be well dried, weighed, soaked in water for an hour, and then dried with blotting-paper and re-weighed. The porous absorption of the stone, and its liability to "shut up" on drug ice, may so he known.

The writer is of opinion that the black rock which occurs north of the railway station at Huntly would make better curling-stones even than Burnock Water. It contains olivine, enstatile, magnetite, serpentine , it is tough, heavy, dense, and very compact.

A still better stone used to lie as boulders, sprinkled over the fields in the vicinity of Portsoy. The rock is so tough that these boulders were locally termed heathens. A Free Church minister took the most of these, not into his fold, but he built his fold of them sufficient have escaped, however, to be experimented on.


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