rest.

SLAG, n. s. Swed. slagge. The dross or recrement of metal.

Not only the calces but the glasses of metal may be of differing colours from the natural colour of the metal, as I have observed about the glass or slag of copper. Boyle. SLAINS, a parish of Scotland, in Aberdeenshire, on the coast of Buchan, about five miles long, and three broad, of a triangular form. The sea-coast extends six miles, four of which are rocky and two sandy. The rocks are high, indented with immense chasms, and abounding with capacious caves. One of these is above 200 feet long, and another, called the Dropping Cave, or White Cave, is covered on the inside with beautiful white stalactites. The surface is

level; the soil fertile; and as gravel, shells, sand. marl, and lime-stone, abound, agriculture is much improved. The ruins of the ancient castle of Slains, which was demolished in 1594 by James VI., on Huntly's rebellion, are still to be seen upon a peninsulated rock. There are also relics of a chapel built in the seventh century, and dedicated to St. Adamnan, the disciple of St. Columba.

SLAKE, v. a. & v. n. From slack.-Skinner; from Island. slock, to quench.-Mr. Lye; Goth. lecka.-Thomson. To quench; extinguish; go out; to grow less loose or relaxed: confounded with SLACK.

Crashaw.

She perceiving that his flame did slake And loved her only for his trophy's sake. Browne. From Iülus' head

A lambent flame arose, which gently spread
Around his brow, and on his temples fed:
Amazed, with running water we prepare,
To quench the sacred fire, and slake his hair.

Dryden. Coarse are his meals, the fortune of the chace; Amidst the running stream he slakes his thirst. Addison's Cato.

That which he saw happened to be fresh lime, and gathered before any rain had fallen to slake it.

Woodward.

sponding.

He hath slandered thy servant unto the king. 2 Sam. xix. 27.

I was never able till now to choke the mouth of such detractors with the certain knowledge of their Spenser on Ireland. slanderous untruths. doubts, and slanderously bark at the courses which I may the better satisfy them who object these are held against that traiterous earl and his adhe

Yet charge the consul with our harms,
That let him go

So in our censure of the state

We still do wander,

And make the careful magistrate

The mark of slander. Ben Jonson's Catiline. They did slanderously object, How that they durst not hazard to present In person their defences.

Daniel's Civil War.

In your servants suffer any offence against yourself rather than against God; endure not that they should be railers, slanderers, telltales, or sowers of dissension. Taylor.

There are not only slanderous throats, but slanderous ears also; not only wicked inventions, which engender and brood lies, but wicked assents, which hatch and foster them.

Barrow.

SLANT, adj. > From Dutch slanghe, a serSLANTING, pent.-Skinner. Swed. slanke, SLANT'WISE. is to slide off. Oblique; not direct; not perpendicular.

Some maketh a hollowness half a foot deep, With fower sets in it, set slantwise asteep. Tusser. Late the clouds Justling, or pushed with winds, rule in their shock, 2 F

SLAP, n. s., adv., & v. a. Teut. schlap; SLAPDASH'. interj. Goth. slap. A blow. Properly with the hand open, or with something rather broad than sharp.

Dick, who thus long had passive sat,
Here stroak'd his chin, and cocked his hat;
Then slap't his hand upon the board,
And thus the youth put in his word.

Prior.

Id.

And yet, slapdash, is all again In every sinew, nerve, and vein. Peg's servants complained; and, if they offered to come into the warehouse, then straight went the yard slap over their noddle.

Arbuthnot's History of John Bull. The laugh, the slap, the jocund curse go round. Thomson.

SLASH, v.a. v. n & n. s. Island. slasa, to strike. To cut; cut with long cuts: lash; to

strike at random: a cut or wound.

The knights with their bright burning blades Broke their rude troops, and order did confound, Hewing and slashing at their idle shades.

Faerie Queene.

His oylet-holes are more and ampler : The king's own body was a sampler. Not that I'd lop the beauties from his book, Like slashing Bentley with his desp'rate hook.

King.

Prior.

Pope. SLATE, n. s. & v. a. From slit: slate is in some counties a crack; or from Fr. esclate, a tile -Johnson. But Sax. rlith is, flat; even; smooth; and a more probable derivation. A gray stone, easily broken into thin plates, used to cover houses, or write upon. See below. To cover with slates.

A square cannot be so truly drawn upon a slate as it is conceived in the mind. Grew's Cosmologia. A small piece of a flat slate the ants laid over the hole of their nest, when they foresaw it would rain. Addison's Spectator.

All the stone that is slaty, with a texture long, and parallel to the sight of the stratum, will split only lengthways or horizontally; and, if placed in any other position, 'tis apt to give way, start, and burst, when any considerable weight is laid upon it.

Woodward on Fossils.

Sonnets and elegies to Chloris Would raise a house about two stories, A lyrick ode would slate.

Swift.

SLATE (stegania), a stone of a compact texture and laminated structure, splitting into fine plates. See MINERALOGY. Dr. Hill distinguishes four species of stegania. 1. The whitish steganium, being a soft, friable, slaty stone, of a tolerably fine and close texture, considerably heavy, perfectly dull and destitute of brightness, variegated with a pale brown or brownish-yellow. This species is common in many counties of England, lying near the surface of the ground. It is generally very full of perpendicular, as well as horizontal, cavities, many of which are filled up with a spar a little purer and more crystalline than the rest; and is commonly used for covering houses. 2. The red steganium is a very fine and elegant slate, of a smooth surface, firm and compact texture, considerably heavy, and of a very beautiful pale purple, glittering all over with small glossy spangles: it is composed of a multitude of very thin plates or flakes, laid closely and evenly over one another, and cohering pretty firmly this is very common in the northern parts of England, and is much valued as a strong and beautiful covering for houses. 3. The common blue steganium is very well known as a useful and valuable stone, of a fine smooth texture and glossy surface, moderately heavy, and of a pale grayish-blue; composed of a multitude of even plates, laid close upon one another, and easily splitting at the commissures of them; this is also very common in the north parts of England, and is used in most places for the covering of houses. There are other species of this slate, viz. the brownish-blue friable steganium, usually called coal-slate; the grayish-black friable steganium, commonly called shiver; and the grayishblue sparkling steganium. 4. The friable, aluminous, black steganium, being the Irish slate of the shops: this is composed of a multitude of thin flakes, laid very evenly and regularly over one another, and splits very regularly at the commissures of them. It is common in many parts of Ireland, and is found in some places in England, always lying near the surface in very thick strata. In medicine it is used in hemorrhages of all kinds with success, and is taken often as a good medicine in fevers. The island of Eusdale, one of the Hebrides, on the west coast of Scotland, is entirely composed of slate.

The localities of common slate are so numerous that it is to attempt almost an endless task to point them out. Roof-slate is found on the western side of our island in the counties of Cornwall and Devon, in various parts of North Wales and Anglesey, on the north-west parts of Yorkshire, near Ingleton, and in Swaledale, also in the counties of Cumberland and Westmoreland. It occurs in a low range of mountains at Chamwood forest, in Leicestershire, near the centre of England. Slate abounds in various parts of Scotland, and in Wicklow, and other parts of Ireland.

mountainous

slate, near Laferriere in Normandy, and in the France possesses many valuable beds of roofneighbourhood of Angers. The last is the most important, as furnishing slate of the most perfect quality, and its extent makes it regarded as inexhaustible. It is further remarkable on account of the very singular and interesting organic re

mains that occur between some of the laminæ. The bed extends for a space of two leagues, passing under the town of Angers, which is built as well as covered with it; those blocks being employed in masonry which are the least divisible. The quarries which are actually explored are all in the same line from west to east, as well as the ancient pits, the bed of the best roof-slate rising to the surface in this direction. Immediately under the vegetable earth is found a brittle kind of slate, which, for four or five feet deep, splits into rhomboidal fragments. A little lower is what is called the building-stone, which is a firm slate, but scarcely divisible. This is employed in the construction of houses, after it has been sufficiently hardened by exposure to the air. At fourteen or fifteen feet from the surface is found the good slate, which has been quarried to the perpendicular depth of about 300 feet; the remaining thickness being unknown. The interior of this great mass is divided by many veins or seams of calcareous spar and quartz, about two feet thick, by fifteen or sixteen in height; these veins are parallel, and proceed regularly from west to east, in a position rising 70° S.; they are intersected by other veins at intervals of a similar kind, but whose rise is 70° N.; so that, when they meet the former, they either form rhombs, or half rhombs, which have been compared to the letter V, some being upright, and others reversed. All the layers, or laminæ, of the slate, have a direction similar to those of the veins of quartz, which rise 70° S.; and, when intersected by veins that have an opposite inclination, the direction of the slaty laminæ is not changed. The whole mass is thus divided into immense rhomboids, composed of plates all parallel among themselves, and with two of the faces of the rhomboid. The slate is extracted in blocks of a fixed size, which are divided into leaves for roofing-slate. It is betwixt these leaves that there are frequently found vestiges of marine animals, and particularly pyritous impressions of pous de mur (the sea-louse, a small univalve shell), also of small cheviettes (shrimps or prawns), and a species of crab, of which the body is about a foot in breadth and fourteen or fifteen inches in length, the tail having nine or ten rings. The shrimps are sometimes so numerous that forty have been counted on a slate of a foot square. None of the animals resemble any known existing species. But the most remarkable circumstance in these impressions, particularly in the large crabs, is, that though there be no sign of the body having been crushed, yet it can scarcely be said to have any thickness whatever. They rather resemble engravings than figures in relievo. A series of these leaves may be compared to a set of books placed upon shelves; and the impressions of crabs, and other marine animals, to engraved plates in the volumes; they do not, in fact, occupy more thickness. It is equally difficult to conceive how the bodies of these animals, though perfectly defined, could be reduced to a simple surface, without thickness.

These slates also present beautiful dendritical pyrites, more than a foot in extent. The pyrites are sometimes in small grains, disseminated,

like dust, upon the surface of the slates, where may also be observed many little stars of selenite. When the blocks of slate have been drawn from the quarry, if they are left exposed to the sun, or the open air, for some days, they lose what is called the quarry water, and then become hard and untractable, and can only be employed as building stone. Frost produces a singular effect on these blocks: while frozen they may be broken with more ease than before; but, if thawed rather quickly, they are no longer divisible: yet this quality may be restored by exposing them once more to the frost; but, if the operation be often repeated, it becomes impossible to reduce them to leaves.

Only one slate quarry is said to be opened in Italy; i. e. at Lavagna, in Genoa; it furnishes slate of an excellent quality, and so impervious that it serves to line the cisterns in which olive oil is preserved. The canton of Glaris, in Switzerland, is the only one in which roof-slate is procured. Roof-slate occurs in Saxony, and in various mountainous districts in the north of Europe; it is found also on the continent of North America; and as it is only a modification of clay-slate, which is an abundant rock, it is probable that its localities are much more numerous than are at present known in alpine districts in every part of the globe.

We believe all the roof-slate quarries at present worked are those which accident has discovered. This neglect is the more remarkable, when we consider the great expense frequently incurred in searching for coal, a substance of much less value in proportion to its weight. The best beds of roof-slate improve as they sink deeper into the earth; and few, if any, are of a good quality near the surface. There cannot be a doubt that many beds of slate, which appear shattered and unfit for architectural use, would be found of a good quality a few yards under the surface; for the best, in many quarries, loses its property of splitting into thin lamina by exposure to the air.

In Great Britain we have heard of but two places where slate is worked as a mine under ground; one is worked in this way by penetrating the interior of the mountain at Place Fell, on the head of the lake of Ullswater, in Cumberland; and another on the western side of Yorkshire, adjoining Westmoreland; in many other situations it is probable that slate might be worked to advantage, in subterranean galleries, similar to those at Charleville; for as this mineral is generally of a better quality at a considerable depth, the expense of procuring it by mining would be much less than that of removing the load of upper rocks, and working it in open quarries.

The mouth of the mine at Charleville is near the summit of a hill: the bed inclines 40° to the horizon: it is about sixty feet in thickness, but its extent and depth are unknown. It has been pursued, by a principal gallery, to the depth of 400 feet; and they have driven many lateral galleries, which extend about 200 feet on the side of the main gallery, where twenty-six ladders are placed in succession, for the passage of the workmen and the carriage of the slate.

In this bed, which is sixty feet in thickness, there are only forty feet of good slate, the other being mixed with quartz. They cut the slate into blocks of about 200 lbs., which they call faix: every workman, in his turn, carries them on his back to the very mouth of the pit, mounting the twenty-six ladders, or a part of them, according to the depth of the bed where he is working. When brought to day, these blocks are first split into thick tables, which are called repartons. The workman holds the block between his legs, puts a chisel on the side, and divides it with a blow of a mallet. The repartons are divided in a similar manner into roof-slates. These operations must be performed soon after the blocks are drawn from the quarry; for, if the stone has time to dry, it would no longer be possible to split it. Some of the slate galleries pass under the river Meuse.

A reddish-purple slate from North Wales contained, according to Kirwan, 38 silex; 26 alumine, 8 magnesia, 4 lime, and 14 parts iron; but, as there is in this analysis a loss of ten per cent., it cannot be considered as very accurate. As the hardness of slate arises principally from the silex it contains, which is of all the earths the least favorable to vegetation, those slates which are the hardest when first taken from the quarry, and which have the least specific gravity, are to be preferred; for the increase of weight in slates is owing to the presence of iron, either in pyrites, or a state of oxide. To the presence of iron, many kinds of stone and slate also owe their tendency to decomposition. The pyrites being decomposed by moisture, and the iron admitting a still higher degree of oxygenation, the surface of the stone swells and peels off, OL falls into an ochrey powder.

Dr. Watson, the late bishop of Landaff, says, the specific gravity of the Westmoreland slate varies in different quarries, from 2797 to 2732 ounces the cubic foot. The effect of frost is very sensible on tiled houses, but is scarcely felt on slated houses; for good slate imbibes very little water. According to an experiment made by him on Westmoreland slate, compared with tile, in which two pieces of each, about thirty inches square, were immersed in water ten minutes, and then taken out and weighed, as soon as they ceased to drop; the tile had imbibed about one-seventh of its weight of water, and the slate had not absorbed theth part of its weight: indeed the wetting of the slate was merely superficial. When placed before the fire, in a quarter of an hour the slate was of the same weight as it had been before it was put into the water; but the tile had only lost about twelve grains of its moisture, which was as near as could be expected to the quantity which had been spread over its surface; for it was the amount gained by the slate, the surface of which was equal to that of the tile. The tile was left to dry six days, in a room heated to 60°, but did not lose all the water it had imbibed till the end of that time. The slate in Westmoreland is blasted from the quarry in large masses, and split with proper tools by the workmen. Though the specific gravity of Westmoreland slate from different quarries is nearly the same, yet all the

sorts are not capable of being split into an equa degree of thinness. Here also the quality varies with the depth of the quarry, that being the best which is raised from the greatest depth. The gray-blue slate from Donyball, in Cornwall, weighs only 2512 ounces to the cubic foot, which is considerably lighter than that of Westmoreland. This slate is generally preferred to any other for its lightness, and enduring the weather; but Dr. Watson is of opinion that in durability it does not excel that of Westmoreland. The Donyball slate is split into laminæ about one eighth of an inch thick, when it is applied to the covering of a roof; it then weighs rather more than twenty-six ounces to the square foot. The pale blue slate from Ambleside, in Westmoreland, weighs about two ounces more in the square foot than the former. In many instances, we believe, slate of a thinner kind is used in several modern buildings, to save the expense of timber in the roof, where cheapness rather than durability is a principal object with the architect. According to an estimate of Dr. Watson, the weights of a covering of the following different materials, for forty-two square yards of roof, are

as under :

A ton of fine slate will cover a larger surface than a ton of lead; and, where there is water carriage, does not cost one-fourth of the price. Slate might, therefore, be used generally instead of lead, with great advantage.-Watson's Chemical Essays, vol. iv.

The most extensive slate quarries in Great Britain are near Bangor, in Caernarvonshire. There is a rail road formed from the quarries to the sea: but perhaps the most remarkable situation in the world where slate is procured is in Cumberland, at Hourston cragg, a lofty mountain near the lake of Buttermere, about 2000 feet above the level of the lake, and nearly perpendicular. On account of the difficulty of access, the workmen take their provisions for the week, and sleep in temporary huts on the summit. During the winter they are generally involved in clouds, and not unfrequently blocked up by the snow. The slate is conveyed down a zigzag path cut in the rock on sledges, one man attending to prevent the acceleration of the descent. When the slate is emptied at the bottom, the sledge is carried back on his shoulders to the summit.

Whitby alum slate has a very dark gray color, a slaty structure, and rather a silky lustre; it splits, by exposure to the atmosphere, into very thin lamina; it varies in hardness, but is all softer than roof slate. The particular advantage which the country near Whitby possesses for the manufacture of alum is derived from the alum slate rising in precipitous cliffs, which afford facilities for working and burning the stone. Though many of the coal shales might yield an equal quantity of alum, the difficulty of raising

them to the surface would in most situations be too great to repay the expense. The alum slate is piled in vast heaps and set fire to; a slow combustion is continued for several months, by the inflammable matter combined with the stone. The saline contents are extracted by solution, a small quantity of potash is added, and the alum is crystallised by evaporation.-Bakewell's Introduction to Geology.

From this alum rock of Yorkshire nearly all the alum of commerce in England is produced. According to Klaproth, alum slate contains:— Sulphur

Carbon

Alumine

Silex

Black oxide of iron

Sulphate of iron, lime, and potash, each Water

0-28

1.96

1.60 4.00 0.64 0.15 0.70

This writer remarks that the sulphur, in the alum slate which he analysed, was not united to the iron, but to the carbon, in a manner at present unknown. In the alum slate of Whitby the sulphur seems combined both with the iron and carbon.

Drawing slate, which frequently accompanies alum slate, is much softer than common slate, and contains, like alum slate, a considerable portion of carbon its color is a grayish-black: it is known by the property which it possesses of leaving a dark line when rubbed on paper. It is soft, and sometimes rather unctuous: some varieties have a small degree of lustre. The fracture, in small fragments, is scarcely slaty, and sometimes approaches the conchoidal. Drawing s ate is easily cut with the knife. Under the blowpipe it turns white or yellow. It sometimes effloresces like alum slate. According to Wiegleb, it contains

This slate is employed by masons, carpenters, &c., to mark with. When fine and pure, it is used by artists for designs. In France it is called pierre d' Italie; in England, French chalk. It is found in France, near Séer, in the department of l'Orne, and in the environs of Cherbourgh. It is found also in Spain and Italy.

Hone whet-slate (novaculite of Kirwan) occurs imbedded in clay slate: and is of a greenishgray color, inclining to yellow; it is much harder than common slate; its texture fine grained, nearly compact, and the fracture of the small pieces splintery or conchoidal, resembling flinty slate. Its specific gravity about 2-72. Translucent on the edges, it does not effervesce with acids, and it melts into a brown enamel under the blowpipe. From its green color, and rather Teasy feel, it may be considered as intermediate between hard talcous slate and clay slate. Though it yields to the point of a knife, or even of a copper tool, it acts upon the flattened or round surfaces of metals, and is used for sharpening and polishing the finer kinds of cutlery. It is

of considerable value on account of this property. The common kind is procured from Saxony; and a finer quality in the promontory of Howth, near Dublin.

SLATING is employed, in architecture, in sundry ways, the principal of which refers to the covering of the roofs of buildings, but such has been lately the perfection of working in slate, that it is now wrought and fitted into many useful utensils, as well as made up into balconies, chimneypieces, casings to walls, skirtings, staircases, &c. &c. The slate principally in use in London is brought from Wales, taken from out of quarries, which are worked on the lord Penhryn's estate at Bangor, in Caernarvonshire, and it is thence forwarded to all parts of the united kingdom. There are also in use some other kinds of slate, the best sort of which is brought from Kendal, in Westmoreland, and is called Westmoreland slate. These slates are of a fine pale bluishgreen color, and are most esteemed of any by the architects. They are not of a large size, but they are of good substance, and well calculated to give a neat appearance to the roof on which they may be placed. The slate brought from Scotland is nearly similar in both size and quality to a slate from Wales, called Ladies, from which circumstance they are very little sought after.

The French slates were very much in use in this country about seventy years since. They are small in size, most commonly not larger than the Welsh doubles, excessively thin, and consequently light; but thin composition has been found not to be well adapted to this climate, where there is an atmosphere containing an excess of moisture. By analysis, this slate is ascertained to contain one-thirtieth of manganese, besides other matters, such as iron, &c., the excessive affinity of which for oxygen soon shivers the stony portion of the slate into atoms, when employed as a covering to buildings in this country. The writer of this article has seen slates of this kind on a roof reduced to the state of powder, having become so by exposure, and appeared to be completely decomposed.

Of the pitch of a roof.--This, in as far as the elevation of the rafters is to be considered, is found to vary in different climates. In Italy. and all the southern parts of Europe, it is made generally less than one-fourth of the span or breadth. In England it was formerly threefourths, but it is now made to approach much nearer to the Italian proportion. In northern climates a steep roof is required, on account of the great falls of snow to which they are liable, and which greatly increase the lateral thrust of the rafters. For the horizontal force exerted by a roof, if it be considered with reference to the walls which sustain it, is in proportion to the length of a line perpendicular to the rafter descending from its extremity till it meets another similar line drawn from the opposite rafter, and this perpendicular is obviously increased when the roof is made very flat. But a flat pitched roof is stronger than a high one for resisting all transverse strains which tend to break the rafters. Slaters class the Welsh slates after the following order and designations, viz.