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340 Dr Herschel's Observations on the Planet Satarda longer in view than it should have and the Earth, is flattened at the done; and as it moves about 2.1 de. Poles ; and therefore ought to be sopo grees in that time, and its orbit is posed to turn on its axis. larger than that of the seventh, the difference is inconsiderable. It is not July 22, 1776. I thought Sacorn wa my present intention to enter into a not exactly round. conlideration of the amount of these May 31, 1781. It appears as if the refractions, otherwise we might pere

body of Saturn was at least as much haps find data enough to subject them

flattened as that of Jupiter ; but as to some calculation. But what has

the ring interferes, this may be been said will suffice to shew, that very

better ascertained eight years hence. probably Saturn has an atmosphere of August 18, 1787. The body of Saa copfiderable density.

turu is of unequal diameters, the The next inference we may draw

equatorial one being the longeft

.. from the appearance of the belts on Sept. 14, 1789, 23 h. 36' 32". HaSatorn is, that this planet turns upon

ving reserved the examination of an axis which is perpendicular to the

the two diameters of Saturn to the ting. The arrangement of the belts, present as the most favourable during the course of fourteen years

time, I measured them with my that I have observed them, has al- twenty-feet reflector, and a good ways followed the direction of the parallel wire micrometer. ring, which is what I have called being equatorial. Thus, as the ring Equatorial diameter, ift meaopened, the belts began to advance

21,94 towards the south; and to thew an

2d

23,11 incurvature answering to the projec

21,73 tion of an equatorial line, or toʻa pa

22,85 rallel of the same. When the ring clo!ed up, they returned towards the

Mean 22,81 north ; and are now, while the ring paff-s over the center, exa&ly ranging Polar diameter, ist measure, 20,57 with the shadow of it on the body;

2d

20,10 generally one on each side, with a

3d

21,16 white belt close to it. When I say, that the belts have always been equatorial,

Mean 20,61 I pass over trifling exceptions, which certainly were owing to local causes. By this it appears that Saturn is The step from équatorial belts to a considerably flattened at the roles rotation on an axis is fo easy, and, in And as the greatest measures were the case of Jupiter, so well ascertain. taken in the line of the ring and of the ed, that I hall not hefitate to take the belts, we are affured that the axis of fame consequence for granted here. the planer is perpendicular to the plane But, if there could remain a doubt, of the ring; and that the equatorial the observations of June 19, 20, and diameter is to the polar one pearly as 21, 1780, where the famne spot was 11 to 10. seen in three different ftuations, would We may also infer the real diame. remove it completely.

ter of Saturn from these measures, There is another argument, of equal which are perhaps more to be depende validity with the former, which now ed upon than any that have hitherto I shall bring on.

I is founded upon been given. But as in my jourpa) I the following obfervations, and will have measures that were repeatedly thew that Saturn, like Jupiter, Mars, taken these ten years past, dot as

3d 4ih

of the diameter of Saturn, but of the great use in ascertaining the quantity ring, and its opening, whereby its in- of matter contained in the planet, I clination may be known ; as well as reserve a full inveftigation of rhcío of the distance of the fourth, and fifth, things for another opportunity. and other fatellites, which will be of

TH

Some Account of the Strata and Volcanic Appearances in the Wefern

Islands of Scotland. In a Letter from Abraham Mills, Esq; to John Lloyd,
Esq; F.R.S.
THE volcanic country, which low spots, where the soil is sandy,

we explored together in the and produces not only grass, but iland of Mull, having hitherto re- likewise corn and potatoes. The maioed undescribed by any traveller, whole extent of the island is three Į shall now beg leave to remind you miles in length N. E. and S. W. and of what we saw there, and in our one mile in breadth ; and it entirely voyage to Staffa.

con Gits of alternate barrea crags and Sailing from Freeport, in the island little fertile vales. of llay, at ten o'clock at night, of Having engaged a boat with four Wednesday, July 2, 1788, we pale rowers, we went from Icolmkilt sed Colonsay, without being able to through the Bull Sound, which runs diftinguish the substance of its shores; between Nun's Island and the island but entering the fouod of lona, we saw of Mull; on both sides the cliffs are that the rude coast of Mull, and the of red granite, ragged and broken, less elevated shore of Iona, was com. without any regular beds or fifluress posed of red granite. Ar the landing and having no particular range or place in Iona is laminated borostone; inclination. Hence we steered for and a quarter of a mile north from the Ardlun Head, which forms the S. W. șuins of the Cathedral is a ve'n of point of Loch Leven. When we coarse red granite, two feet wide, approached the Head, we stopped standing nearly vertical, and ranging the rowers, and sat some time conwith the hornitone E. N. E. and W. templating the wonderful arrangeS. W. on the surface are tumblers of ment of the basalt columns; and red granite, and some few of lava. as we again rowed along there About a mile N. W. from the Ca- to the eastward, had a fine view thedral, and near the shore, is a vein, of the various fituations into two feet wide, containing feldspath which the columns were thrown. and white mica, ranging E. and W. The coast being every where steep, between granite sides. Many of the it was some time before we could rocks are tinged with iron, and there find a convenient place to land , is some bog iron ore in the moffcs. but having at last gor on snore, we In the S. W. part of the island, is a walked to the extreme point or head : body of white marble, veined with here, Iruck with the errors of our pale green. At the Cove, where it maps, which placed the islands in is said St Columb landed, the cliffs fighe very differently from their true are of red granite, and the shore is situations, I took the following bear covered with great variety of pebbles ings by the compass. of serpentine, basaltes, granite, quartz, The N. E. point of Iona N.W. by W. and other subftances. The N. W. The Dutchman's Cape N.N.W.part of the Illand is very rocky, Cairnborough N. by W. - Staffa afording little pasture, except in some from N. to N. w. diftant, by efMr Mills's Observations on some Strata in Scotland. timation, about three leagues.-Rhu not so close as those of the Giant's Thalve, the northernmost extreme Causeway ; but, like those, their topse of Mull, N. by E.-Inch Kenneth where exposed, are either concare or N.E. * N.-The point of Ben Vaw. convex. ruch, on the north side of Loch At the extremity of the glen is an Leven, N. E. distant, by estimation, insulated rock, supported by basalt three miles. The range of Loch pillars, which are somewhat curved Leven E. by S. and w. by N. and inclined. Incumbent on these

timation rom the Sange.

About a quarter of a mile from the are other pillars, lying nearly horie spot where the bearings were taken, zontal, and having a rude face of lava is a deep glen, running N.N.E. to to the westward. At high-water this the sea. It is about thirty yards in rock is inaccesible without a boat; length, and ewenty in breadth. The but at low-Water it may be easily got ftrata are disposed in the follow- at, by stepping from one tumbler to ing extraordinary manner :-The up- another; and on the north side it is permost is ten yards of lava, with ho- not difficult to clisib to the top. Tho rizontal divisions and verticle joints, bottom of the glen is covered with taking the form of rude pillars. Un- large tumblers of lava the whole way der this is an horizontal bed of a per- down to the rock, and presents the fe&tly vitrified substance, which appears rudest scene imaginable. to have been a fhale, and is from one Opposite Ardlun Head, on the to two inches in thickness. Beneath north side of Loch Leven, is Ben this, is about three yards of a filice- Vawruch, an high promontory, whose ous gravelly concrete ; below which trata are io horizontal beds ; and the are horizontal beds of indurated marl, bill being of a circular figure, gives it of various thicknesses, from six to the appearance of several terraces, with twelve inches. The whole of these a kind of castle or cairn on the top. beds, taken together, are about four The columnar pillars at Ardlug yards, and there is a large fiffure in are more or less regular for an extent them, on the west side of the glen. of near a mile and an half; and all Lastly, are ten yards of rude lava, the projecting points of Loch Leven, containing fpects of quartz and mica as far as the eye could reach, appearunaltered, pieces apparently of gra- ed to be composed of lava. site, and somenodules of calcined chert. Amongst the rude lava, which *The whole is incumbent on regular ba- forms the basis below high water mark, fale pillars, of various dimensions, are nodules of crystal and agate, ado from eighteen to fix inches diameter, hering in small lumps to the rocks s varying in the number of their fides, but, being blackened by the washing some having five, fome fix and others of the fea, are not to de discovered feven fides. They are also as vari- without a very nice search. Our ously difposed; those on the western boatmen informed us, that higher op extremity of the glen being straight, the Loch there is a bed of coal. This and lying horizontally ; whilst of those we withed to see ; but, as they also on the east side some are bare, and told us, that the weather, which bad standing perpendicularly; and others, for some days palt been very tempefwhich are furmounted by the rude tuous, was now favourable for landing lava, are inclined and curved, as if on Staffa, we determined to avail they had taken that form in cooling ourselves of the opportunity, and got from the pressure of the incumbent into the boat, highly pleased with weight. Many of the pillars are what we had seen; and for which very full of bladder-holes: the arti- pleafure we were indebted to the hint Eulations of the joints are close, though in Dr Johnson's Tour to the Hebrides,

W.

by W.

We landed without difficulty on quently feen, and the vegetable foil is the eastern side of Staffa, and on an a decomposed lava. In some places eminence, near the center of the we met with ġravel containing pebilland, I observed the following bles of basaltes, of red granite, and bearings, The Dutchman's Cape of quartz, whose angles were worn N. W.-- Cairnborough N. by W.-off

, and they were become round and The Paps of Jura (over Mull) S. smooth. On the N.W. side, the cliff

has lately given way; a large portion The greatest extent of the island is of it has lately fallen into the lea, and about one mile from N. E. to S. W. a fill further part appears likely to and in one pare not more than a quar. follow it. ter of a mile from S. E. to N. W. On the island are two springs of It is tolerably level, the shore every excellent freib-water. There were where fteep, and the cliffs formed by three houses (July 5, 1788) uninhabasalt pillars or rude lava. The usual bited ; and barley, oats, tax, and landing parts for boats is in a small potatoes, growing near the center, Cove on the N. E. side of the island ; and good grass in several spots. When but we were affured, that there is no the crops are ripe, labourers are sent anchorage for vessels round its whole to gather them in; after which, thircoast. On the south side, rising from ty head of cattle are sent to winter in a nearly horizontal bed of reddish the ifland, which, with a solitary Itone, are beautiful basalt pillars of herdsman to attend them, continue considerable height, and standing ver- till feed-time the ensuing spring. tically; at a little distance are others In attempting to return to llay, after inclined, and others which are cur- having got within three miles of the ved, 'very fimilar to the ribs of a N.W. part of Colonsay, av heavy gale Thip. There are three caverns amidit of wind came on, which obliged us to the basaltic piilars; the northernmost bear away, and take shelter in the goes in to the eastward, how far I Bull Sound. The weather continuing know not; for, though we weot en- stormy, we landed, and walked to tirely round the island in our boat, Fidden, the house of Lieut. Colonel the tide was too high, and the swell Campbell, of the Plymouth division too great, to permit our entering any of Marines, who received us with the of the caverns without the utmolt utmost cordiality, and hospitably enrisk; we therefore forbore to make fo. tertained us foi five days, which we dangerous an attempt. One of the were detained by an adverse wind and caverns is now usually called Fingal's severity of weather. Availing ourCave; but the school-master at Icolm- selves of this delay, and of Col. Campkill informed us, that the Erfę name bell's polite offer to be our guide, for it is Feio, which fignifies the me. we set out on foot with him and lodious or echoing cave. On the Lieutenant Stewart, to view the seam Durthern part of the land, and at the of coal on the south side of Loch cure where we landed, the cliffs are Leven. After palling fome noory of coarse lava, without any pillars. ground, and continuing our route to la fume parts of the island the tops the northward for an hour and an of the pillars are standing bare ; in half, we came to a spot where the cther

parts the sur ace is formed by rock which puts up to the day is a a rude argillaceous lava, full of blad- laminated micaceous stone of the gneiss der-holes, fome empty, others replete kind (Kịrwan, p. 102.) and in anowith quartz crystals. Calcareous spar, ther half hour, near a small town on pebbles of indurated clay and fhoerl, the S.W. side of Loch Lyne, we were Jecashed pieces of zeolite, are fre. Shewn a quarry where the gneiss ran. i

ges

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part of

Mr Mills's Observations on some Strata in Scotland. ges N. E. and S.W. and has a flight feet below the surface. At the baclo hade to S.E. It is in ribs from two of the house, towards the sea, are to twelve inches thick, and is ftrati. cliffs of red granite, which extend fied by intermediate ribs of red gra- rourid 10' the Buti Sound. On the nite of about an inch thick. We cros- shore are pebbles of basaltes, of grased Loch Lyne in a boat, and land- nite, and of gneiss; and from the ed on the rude mass of lava, which firm rocks we collected several specicontinues away to the N.E. by the mens of grapite, in which the feldtown of Ardlun, and onwards to the spath, quartz and black mica, are dif. S.W. Gde of Loch Leven.

feien ly blended' but without any In a small bıy, about one mile to fhoerl. the S. E. of Alulun Head, under a During our stay at Fidden, I bed of jointed lava, 'wiich has fome leaned from Mr Siewart, that Rbos resemblance of pillars, and just at Mull, which is the N.W. high-water mark, is a bead of coal, Mull, is chiefly ied granite: in the ex ictly twelve inches thick, int rmix. southern part of the island is very fine ed with de or bituminous fhistus white freelle ne, and between that and (Kirwan, p. 89.) dipp og S.E. towards the granite all whynstose. The the Loch one yard in ihrer : there is ifl ind of Lismor“, in the sound of not any invervening fu stance btreea Muli, is entirely limeftne, excepto the coal and the supericumbent Java, ing where it is ci offed by the Whya which contains mary bladder holes. Dykes. In the illand of Ulva are Beneath the coal is alto lava without pillars somewhat resembling those of any intervenin; marier. About twen Steffa, but of a paler colour.-Canty yards to th: NW. the coal again na aiso is basaltic, and resembles Staffa. appears in the cliff, but is not more - The Duchman's Cape has rude pile than frim eight to ten inches thick. lars.-Carnborough the fame. DunHere are tumblers of various sizes, vegan in the isle of Skye has basalsca tered on the shore. Amongst them tic pillars, similar to Staffa.-O. are some resembling the Derbyshire the sou:h-west side of the isle of Egg toad ftoae ; and a Muri distance inland is a curious cavern. (to the S. W.) are rude masses of lava, We agiin embarked for Ilay; bot, itaning up at day, not unlike the it being calm, and the tide against us, grea: Whyn Dykes of Ilay. In the were obliged to anchor; and we landLoch, and sóme distance from the ed on an island which forms the S.E. opposite în re, there ftood, within point of the sound of Iona. From the memory of man, an insulated the point, which is a bare rock of red pillar of coal, from which the coun- granite, broken and jointed in every try people were accustoined to pro- direction, I oblerved the following cure a supply for smiths ufe ; but the bearings. lcolmkill Church N.N.E. quantities they carried away, and the — The northermoft part of Staffa, continual washing of the lea, have over the N.E. point of the found of now entirely removed it.

Iona, N E. by N.-Tie south Pap We returned to Fidden House, of Jura, cver Colonsay, S. which is fituated on level grourid The upper furface of the granite, near the fea, and near a small Loch, even in the very highest pari, is all which affords a harbour to small vera convex, which seems to prove, that sels, but is dangerous to enter. The by some convulfon ie has been thrown flat country in front of the house is up from the bed of the ocean. which, entirely composed of sea fard, includ. by long washing over it, had preriing shellswhen dug into, fich ously worn down its fubftance at the water is constantly found at a few edges of all its numerous joints. Os

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