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if the biddings are not sufficiently low, to offer the bargain on their own terms, or to withdraw it altogether. The work is divided into Tutwork, or work done by measure, at a certain rate per fathom; Tribute, ore raised and paid for by a certain proportion of its value when sold; and Dressing, an agreement for picking over again at a higher rate the refuse of the tributers. The Tutwork is let by bargains, requiring from four to twelve men, who are collectively called a pair of men ; the Tribute, in pitches, or limited spaces of ground, on which two to six men are employed; the Dressing generally affords employment to the women and children. Tools are delivered to the person taking the work, for which, and for the gunpowder, candles, and cash advanced, his account is debited.
The ore delivered by the tributers, is turned over to the public parcel by the captain, after samples have been taken by the miner, and on the part of the adventurer. A sample is assayed for the latter by the assay master of the mine, according to which the value of the portion is estimated when the whole is sold. This sale is also conducted by samples taken from the public parcel, divided for mutual convenience into a number of lots, called Doles, containing from fifty to a hundred and fisty tons each. The samples of copper are distributed to the agents of the different copper companies, three or four weeks before the sale takes place, when they attend and make their biddings by ticket according to the assay, the market price of copper, the quantity of ore on hand, and the quality of the ore, with respect to the purposes for which it is wanted. In this manner, seventy to a hundred thousand tons weight of ore, producing on an average about 8 per cent. of pure copper, have been sold annually in Cornwall, for something more than half a million of money, besides the produce of fourteen or fifteen thousand blocks, or forty to fifty thousand cwt. of tin.
Of the magnitude of the undertakings some estimate may be formed, when it is recollected that several mines afford employment to more than a thousand hands. With respect to the advantage of these enterprises to the proprietors, Mr. Taylor is of opinion, that
• Mining, on the whole, does not yield any great profit to the adventurer, though there are numerous instances of extraordinary gain ; these are probably nearly balanced by more numerous corcerns, in which loss is incurred: the latter, however, if taken individually, being generally much less in amount than the former.'
Their effect in supplying the population with means of subsistence, and their influence upon the morals of the lower class, do not come within the scope of a work like that before us;
our own observations, however, incline us to suspect, that on the whole they are not beneficial. The precariousness of the employment encourages a spirit of speculation ; and a presumption on future gains to make up for present extravagance, which undermines the domestic happiness of the miner. The enterprise which to-day affords him subsistence, may, without warning, become unproductive, and himself, with his companions, be compelled to seek work elsewhere: he has, therefore; no encouragement to expend his money in multiplying the comforts of his habitation, or in acquiring any kind of property which does not adınit of easy removal from place to plaee: With vigorous and exercised understandings, their dwellings are mere hovels of barbariaus; and while their ingenuity and industry do vot admit of a doubt, it is equally certain that the poor rates of the mining districts are as high in proportion as in the crowded manufacturing towns.
XV. On the Origin of a remarkable Class of Organic
Impressions, occurring in Nodules of Flint. By the Rev. William Conybeare.
The impressions, or rather casts, whose origini Mr. Conybeare investigates with acuteness and accuracy in this paper, have occasioned much difference of opinion among collectors of fossils. They appear in the form of flattened tubercles, connected by lateral filaments on the surface of fragments of flint, and were undoubtedly moulded in the cavities and perforations, made by some marine animal, in various shells. The substance of the shell being removed after the injected siliceous matter had acquired consistency, these casts present figures in relief. The amygdaloids are similar casts in cavities, made by the Pholas in madrepores : indeed, had Mr. Conybeare pursued the subject farther, he might have traced protuberances and filaments of a similar origin in all rocks in which the testaceous remains have been removed, and their place not yet occupied by infiltrated matter. XVI. A Description of the Oryd of Tin ; of the primi
tive Crystal and its Modifications ; including an Attempt to ascertain with Precision the Admeasurement of the Angles, $c. By William Phillips.
This paper is a valuable contribution towards a natural history of Tin, and does great credit to the patient research and acute observation of the Author. The idea of native tin has been entirely given up, the specimens preserved as such, being proved to have undergone the action of fire in neglected smelting houses. The oxyd, crystallized and in a compact state, and the sulphuret or bell metal ore, are the only species known in Cornwall. The former occurs in combination with a great variety of other minerals. Mr. Phillips mentions as its attend. ants,---Granite, Schist, Chlorite, Schorl, Carbonate of Lime, Topaz, Chalcedony, Fluate of Lime, Yellow copper ore, Blende and Quartz, Mispickel and Wolfram. Its specific character is given as follows :
• Primitive crystal.-An octoedron composed of two obtuse quadrangular pyramids joined at their bases, which are square. Fraca ture-mostly shattery, often vitreous ; sometimes conchoidal, some. times lamellar. Aspect--not metallic. Specific gravity 6, 56 to 6,98. wood tin 6,45. Hardness—brittle, and easily frangible; gives sparks with a steel. Electricity, the coloured portions, when placed in communication with an electrified conductor, emit bright sparks on the approach of the finger. Colour-whitish, either translucent or opaque ; it is sometimes of a resin yellow, but more often of a deep brown somewhat reddish, more frequently blackish or black; occasionally brick red, but, in that case generally bears, in some respect, marks of having been exposed to the action of fire. Trangparency-the more colourless crystals are generally somewhat transparent, in which respect they sometimes almost equal common quartz. Lustre resinous or vitreous. Dust-of a dull ash grey. Analysis77.5 tin, 21.5 oxygen; 0.25 oxyd of iron, 075 silex. Under the blowpipe it decrepates; becomes pale and opaque ; is reducible in part to a metallic state, but with difficulty. When heated and melted with glass, it imparts to it a milk-white colour.' pp. 350, 551.
In tracing the primitive crystal through its various modifications, of which Mr. P. enumerates twelve, comprising near one hundred and eighty different figures, independent of macles, macles of macles, and double maoles, he makes use of the reflecting Goniometer of Dr. Wollaston, but with some improvements to render it more accurate: he does not, however, apply calculation to verify the results, which differ in some respects from those of Haüy.
XVII. On some new Varieties of Fossil Alcyonia. By
Thomas Webster. These organic remains occur in the green sand stratum and beneath the chalk in the beds of limestone belonging to it, and were noticed by Mr. Webster at Under Cliff, in the Isle of Wight. They appear to comprise several species of one common genus, but we much doubt whether that genus ought to be denominated Alcyonium, if identity of name implies any resemblance to the recent zoophyte which bears that appellatior. A similar tulip-shaped pedunculated fossil occurs also in the same stratum, among the siliceous casts of Black-dawn and Halldawn, in Devon ; but it is not practicable there to trace the peduncles to that length which Mr. W. appears to have done.
XVIII. Miscellaneous Remarks aecompanying a Catalogue
of Specimens, transmitted to the Geological Society. By
J. Mac Culloch. XIX. Remarks on several Parts of Scotland, which exhibit
Quartz Rock, and on the Nature and Connexion of this Rock, in general. By J. Mac Culloch.
Jameson's Tour to the Western Islands, has, among others, contributed to render the geology of that part of Scotland, in some degree familiar ; but while the united efforts and repeated observations of so many, are still wanting to bring the science to a tolerable degree of accuracy, we cannot wonder that a traveller of such exercised abilities, and such energetic boldness of thought, as Dr. Mas Culloch, should find ample gleanings. The precision with which his remarks are laid down, the fearlessness with which hypotheses are set out of sight, and apparently contradictory facts stated, and the philosophic coolness with which systems are stripped of their tinsel decorations, to examine the foundation on which they really stand, render these observations models for the manner in which mineralogical and geological memoranda ought to be drawn up. They occupy nearly a hundred pages of the volume before us; and are in so condensed a form, that we can indulge in extracting a few only of the most interesting facts.
The Island of Rum possesses strata of a basaltic amygdaloid, the cayities of which are filled with chalcedonies of various colours, some of which are perfectly green from a mixture of green earth ; and these Dr. Mac Culloch identifies with the heliotrope, commonly called oriental, which has long been improperly ranked among the jaspers.
The Craig of Ailsa, a mountain about two miles in circumference, and rising to the height of near a thousand feet from the bosom of the sea, consists of une immense mass of syenite, composed of white felspar and transparent quartz, mixed with black horn-blend.
• This rock is in general amorphous, but in many places it approaches an obscure columnar structure, and this occasionally acquires great regularity. It is on the north west side that the columns are most perfect. They vary in the number of their sides, but like basaltic columns, the most general forms are the pentagonal and hexagonal. I could not any where perceive that they were jointed, but they break at right angles to their axes, forming those Hat summits which are tenanted by clouds of gannets. Their die mensions are universally large, as they are from six to eight feet in
diameter, and extend in height, as far as the eye can judge, to a continuous altitude of 100 feet and upwards. Nothing can exceed the magnificence of the columnar wall on this side of the rock; even the high faces of Staffa sink into insignificance on a compa. rison with the enormous elevation and dimensions of Ailsa. With that elevation is combined an air of grandeur, arising from the simplicity of their aspect, which the pencil and the pen are equally incapable of describing. To the lover of picturesque beauty, they possess a requisite, of which the want is perpetually felt in contemplating the basaltic columns of Staffa or Egg. i his is their gray colour, catching the most varied lights and reflections, when the iron cliffs of basalt are confounded in one indiscriminate gloom. He is an incurious geologist, or a feeble admirer of fine naturę, who is content to pass Ailsa unseen.' pp. 418, 419.
The granite masses on the summit of Goatfield, on the island of Arran, are magnetical, affecting the poles of the needle in situ, and influencing it also even in detached pieces. The circumstance has been observed in the Harz, in Saxony; and Dr. Mac Culloch informs us in a note, that he has since observed it in the mountain Cruachan. Were sufficient attention paid to this interesting phenomenon, it might perhaps prove of more frequent occurrence than is at present supposed.
The graphic granite of Portsoy, long noted for its beauty, has acquired celebrity from the arguments which Dr. Hutton drew from it in support of his theory, imagining that he had proved that the crystallization of its parts, must have been simultaneous. Dr. Mac Culloch produces specimens completely confuting this assumption, and proving a sequence of epochas in the formation of the rock :-but lest the disciples of Werner should glory in the overthrow of their antagonist, he
presents them with a curved detached crystal of schorl, and another crystal of the same substance, passing through the centre of a garnet, the whole suspended in the quartz. Since crystals are never formed curved, and schorl does pot admit of being bent, unless softened either by heat or some other solvent to us unknown; and since, in the second case,
• The schorl crystal must have been supported in a fluid of equal gravity, possessing no action, chemical or mechanical, on it, while a garnet was allowed to crystallize around it; and that this extraordinary state of things must have continued during the time which it would require to deposite a mass of quartz from a watery solution around the whole,' –
we conceive that a confession of ignorance would be the most honourable method of getting out of the dilemma.
Dr. Mac C.'s remarks on the stratification of the neighbourhood of Crinan, which consists of alternating beds of grau.