|
 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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