Sivut kuvina

very heavy; the gardeners would the course of the night, and early not begin their work in due time; in the morning, as they would rebut even if we suppose them to beceive from the sprinkling of the active and attentive, the absorbents water-pot throughout the whole of the leaves and fruit would take day.” up ten times as much moisture in

Account of the DISCOVERY of Silvek in HERLAND COPPER-Mine.

By the Rev. MALACHY HITCHINS. Communicated by the Right

Hon. Sir JOSEPH BANKS, Bart. K. B. P. R. S. (From the PhilOSOPHICAL TRANSACTIONS for the Year 1801. Part 1.) HER TERLAND mine is situated gradually, and terminate, to all ap

in the parish of Gwinear, pearance, at a short distance, comabout scven miles N. E. of St. pletely and irrecoverably, Michael's Mount, on the southern This mine was worked about coast of Cornwall; and two iniles twenty years ago, when it was and a half from the mouth of the sunk to the depth of one hundred river Hayle, on the northern coast fathoms from the surface. It was of the same county: it is conti- again set to work about eight years guous to Prince George mine. sincc;, has now four fire-engines

“ It commences in a valley on and two steam-whims on it; and is the west, and passes through a hill, sunk to a depth of one hundred and which is first of steep and then of fifty-five fathoms below the surface, moderate ascent, for upwards of or, as the miners call it, from grass. half a nuile eastward; when the " It is in this latter period of its principal copper lodes, which fole history, that a discovery has been low this direction, meet with a made of a considerable quantity of large cross lode, by which and by silver ore, in a particular part of other cross courses and flookans, the mine, the singularity of which which intersect them in their fur- discovery, in this country, has ther progress, they are repeatedly much excited the curiosity of the heaved, and so disordered by these public. heaves, in their form and position, For, although the numerous and so changed by them, in respect veins of lead in Cornwall are richly to their composition, as hardly to impregnated with silver, and oc. be recognised.

casionally yield small quantities of The strata of the district in silver ores, and even specimens of which this takes place, consist of native silver, yet, hitherto, no in. the common metalliferous sort of stance had been known of their argillaceous slate called killas. yielding this precious metal in such

The copper lodes of this dise abundance; nor had any circumtrict are remarkable for the short stances, in the natural history of the pess of their continuity: for, mineral veins of this country, borne whereas other lodes may be traced any analogy to those which acto an indefinite extent in the same companied the present discovery, line of direction, these, on the con, These circumstances there, trary, are observed to taper away fore, having been examined with

more attention than usual, shall be saving; and those of the coppe stated with as much precision as it lode are niuch less productive of is possible to obtain, from the re- copper than at a little distance port of those practical miners only from this point. Moreover, the who have hitherto inspected them. the copper lode, in the vicinity of

• The facts which deserve to be the intersection, seeing to have first noticed are, the confined and been influenced by the same causes insulated position of the mass of of improrement and declension as silver ore; its great depth from the cross lode; being richer or the surface of the mine; and its poorer in copper, as the latter was, éontiguity to a copper lode. at a correspondent level, in siler.

• The lode in which it occurs " The richest mass of siltér ore is one of those cross courses, as was found at the depth of two they are here called, which inter- fathoms above the level at which seci and derange the copper lodes, it disappears. and consequently are of a more re- " After this brief account of the cent formation.

most striking facts, it may be pro« Lodes in this direction are per to enter into a more particular usually filled with quartz, but description of the two lodes which frequently produce galena ; and appear, by their intersection, to sometimes, instead of galena, sul lave generated this body of extraphurated antimony. They appear neous matter. here to conform to the same laws, “ The copper lode bears nearly except in the particular instance cast and west by the compass; the now to be described, which forms, cross lode nearly north and south, indeed, a very remarkable excep- or at right angles to it. tion.

" The former is about two feet “ No ores in silver were obe broad, on an average: and it dips servable in this lode, until at the 'ör underlies south, cne toot in a depth of one hundred and ten fathom. The breadth of the latter fations from the surface, of cighty is about two feet and a half, on an below the adit or level; and, at average; and its underlie is east, the further depih of thirty-two fa- about eight inches in a fathom. thoms, they disappeared.

" The heave of the copper lode “ They have been discovered is about eighteen or twenty inches only in the neighbourhood of one to the right, in the language of the of the intersected copper lodes, ex- Cornish miner; the expressioa tending no where above twelve being so far appropriate and confeet from this lode, on the north, or tenient, as it refers to the usual above' thirty-two feet from it, on situation of the observer in the the south, and acquiring this their heaved lode, greatest extent at the deepest * The copper lode is filled with level ; for, the usual dimensions of layers of ore and stony matter, the the silver ore are not more than six laiter of which is here called cupte ; feet in the former situation, and but the oré is usually found contwelve feet in the latter.

tiguous to the walls of the lodde. " It is remarkable; that at the ** The contents of the cross lode point of contact or intersection, arc more singular, in respect 18 ihe contents of the silver lode are their local position, and more vari so poor as to be scarcely worth ous. Only the eastem side of it

products bismuth, grey

produces silver ore, the breadth of extent of their speculation is limited which is, in general about six or by the great depth of the present eight inches, although in some workings; for, forty-five fathom's places it is greater. The other have been sunk since the first dispart of the lode is chiefly composed covery of the silver ; and twenty, of quartz, intermixed with iron, or twenty-five fathoms more, are manganese, and wolfram, together as much as can be sunk in this with a small portion of cobalt and mine, with its present mechanical antiinony.

powers of drawing the water; at The silver ore, strictly speak- which level, viz. one hundred and ing, is a mixture of galena, native eighty fathoms from the surface, it

cobalt ore, vitreous would be somewhat deeper than silver ore, and native silver; which, any mine in Cornwall, and about in respect to their proportions, fol- one hundred and thirty fathoms low the order in which they are here below the level of the sea,

at low enumerated, the galena being the water mark, most prevalent. The native silver, • The other cross lodes in this of which specimens of the greatest mine produce no silver; most of beauty have been reserved for the them being flookans, or lodes cabincts of the curious, is found which are essentially different from chiefly in a capillary form, in the the argentiferous cross lode, in the natural cavities of the lode.

nature of their constituent mass. About one hundred and cight There is one, however, in the easttons of this ore have been raised. ern part of the mine, which, from The miners continue to sink near its resemblance to that, is thought the same point of intersection; and likely to produce silver, whenever seem confident that both lodes will it shall be explored to the same soon become richer, because simi- depth, at its point of intersection; lar instances of declension and re- although these hopes may probably covery have frequently occurred in be fallacious, for the argentifcrous the copper lodes of this mine, and lode intersects five other copper because the two lodes appear to lodes, viz. two on the north, and have a reciprocal influence on cach three on the south side, without other,

producing any silver." “Unfortunately, however, the

CONCLUSION of Dr. Herschel's OBSERVATIONS to investigate the

NATURE of the Sun.


ROM these two last sets of think we may reasonably conclude, establishes the scarcity of the lu- ference in the emission of light and minous clouds, while the other heat from the sun. It appears to shows their great abundance, I me, if I may be permitted the me

K 4


taphor, that our sun has for some jection, if it were shown that a time past been labouring under an another country the weather had indisposition, from which it is now not been so favourable. And, if it in a fair way of recovering. An were generally found that our proapplication of the foregoing me- gnostication from solar observations thod, however, even if we were held good in any one given place, I perfectly assured of its being well should be ready to say that, with founded, will still remain attended proper modifications, they would with considerable difficulties. equally succeed in every other si

We see how, in that simple tuation. instrument the barometer, our ex- “ Before we can generalise the pectations of rain or fair weather, insluence of a certain cause, we are only to be had by a considera- ought to confine our experiment to tion of many circumstances, besides one permanent situation, where its actual elevation at the moment local circumstances may be supof inspection.

posed to act nearly alike at all "" The tides also present us with times, which will remove a number the most complicated varieties in of difficulties. their greatest elevation, as well as “ To recur to our instance of the in the time when they happen on tides, if we were to examine the the coasts of different parts of this phenoinena which they offer to our globe. The simplicity of their inspection in any one given place, cause, the solar and lunar attrac- such as the mouth of the Thames, tions, we might have expected, we should soon bc convinced of would have 'precluded every ex- their agreement with the motion of traordinary and seemingly discor- the sun and moon.' A little redant result.

flexion would easily reconcile us to “ In a much higher degree, may every deviation from regularity, by the influence of more or less light taking into account the direction and heat from the sun, be liable to and violence of winds, the situaproduce a great variety in the se- tion of the coast, and other circumverity or mildness of the seasons of stances. Nor should we doubt different climates, and under dif- the truth of the theory of the tides, ferent local circumstances; yet, though high water at Bristol, Li, when many things which are al- yerpool, or Hull, should have been ready known to affect the tempe- very deficient, at a time when, in rature of different countries, and the place of our experiments

, it others which future attention may had happened to be uncommonly still discover, come to be properly abundant. combined with the results we pro- Now, with regard to the pose to draw from solar obseiva: effect: of the influence of the sun, tions, we may possibly find this we know already, that in the same subject less intricate than we might latitudes the seasons differ widely apprehend on a first view of it. in temperature: that it is not hot

is it, for instance, we should test al noon, or coldest at midhave a warin summer in this coun- night; that the shortest day is try, when pienomena observeri in neither attended with the severest the sun indicate the expectation frosts, nor the longest day with of it, I should by no means con- the most oppressing heats; that wider it as an insurmountable ob- large forests, lakes, morasses, and




swamps, affect the temperature pected, considering our present one way; and rocky, sandy, gra- inquiry, which would require comvelly, and barren situations, in a plete observations of every spot, contrary manner; that the seasons great or small, that has been on the of islands are, considerably diffe- sun during such periods as will be ent froin those of large continents, examined. and so forth.

“ With regard to the contempo“ But it will now be necessary rary severity and mildness of the to examine the accounts we al- seasons, it will hardly be necesready have of the appearance and sary to remark, that nothing dedisappearance of the solar spots, cisive can be obtained. But, if we and to compare them with the tem- are deficient here, an indirect perature of the respective times, source of information is opened to as far as history will furnish us with us, by applying to the influence of records.

the sun-beains on the vegetation of The first thing which appears wheat in this country. I do not from astronomical observations is, mean to say, that this is a real erithat the periods of the disappear. terion of the quantity of light and ance of spots on the sun are of heat emanated from the sun; much much shorter duration than those less will the price of this article of their appearance; so that, if completely represent the scatcity the symptoms which have been or abundance of the absolute propointed out, as denoting the state duce of the country.. For the price of the sun with regard to light and of commodities will certainly be heat, should be well founded, we regulated by the demand for them; ought rather to look upon the ab- and this we know is liable to be sence of spots as a sign of defi- affected by many fortuitous circiency, than on their presence as cumstances. However, although one of abundance; and this would an argument drawn from a well justify my expression, of thc reco- ascertained price of wheat, may 'very of the sun from an indisposi• not apply directly to our present tion, as being a return to its usual purpose, yet, admitting the sun to splendor.

be the ultimate fountain of fertility, In going back to early obser- this subject may deserve a short vations, we cannot expect to meet investigation, especially as, for with a record of such minute phe- want of proper thermometrical obnomena as we have attended to. servations, no other method is left The method of viewing spots on for our choice. the sun, hy throwing their picture, Our historical account of the in a dark room, on a sheet of disappearance of the spots in the white paper, is not capable of deli- sun, contains five very irregular cacy; nor were the direct vigw's, and very unequal periods *. The of former astronomers so distinct first takes in a series of twentyas, in the present improved state one years, from 1650 to 1670, both of the telescope, we can have included. But it is so imperfectly them; a very imperfect account recorded, that it is hardly safe to of solar spots may therefore be ex: draw any conclusions from it; for

" * See Astronomic par M. de Lalande, s 3235."


« EdellinenJatka »