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the quartz of the granite, a tolerably good soil is produced sufficient to bear corn crops when properly cultivated and manured.

From granite he proceeded to gneiss, and showed them the difference between the two rocks, although composed of nearly the same sort of materials, namely, felspar, quartz, mica, and hornblende; pointed out to them how granite was granular, and gneiss was granular and slaty; and how that a great part of the Highlands of Scotland is composed of strata of gneiss, and that vegetation, in those districts where gneiss abounds, is generally thought to be more productive than where granite abounds. He next showed them specimens of mica-slate, telling them that they were composed chiefly of mica and quartz, and that Ben-Lomond, Ben-Ledi, and other parts of the Grampian Mountains, were mostly composed of it. He showed them two varieties of it; one abounding with garnets, the other without them. Next followed specimens of clay-slate from various slate quarries in Scotland, such as Aberfoil, Callender, and other places where roofing slate is found; in some slates iron pyrites abound, others are without them. On the banks of Loch-Lomond it may be seen dipping into the water, and rising again on each side of the loch; and may be compared to “a bornie blue ribbon" thrown across the breast of the Grampians.

Next followed primary limestone, quartz rock, and serpentine. Primary limestone, he told them, was sometimes called statuary marble, and that some beautiful specimens of it were found in the North of Scotland. It is of a granular and crystalline texture, and some kinds of it take a very fine polish. Much of the marble that was used by the ancients was obtained from Mount Pentelicus in Attica, and also from the Island of Paros, as well as from Mount Hymettus, Lesbos, and other places; and much that is used by the moderns is obtained from the quarries of Carrara. Quartz, he told them, was also found in the primary formation, and there were many varieties of it. The Cairngorm stone, or rock crystal, is one variety of it; and the common, or amorphous, quartz is another. He also showed them some beautiful varieties of serpentine rock from Portsoy; a rock composed chiefly of magnesia, silica, and iron. After making them acquainted with the order of superposition of the rocks of the primary formation, and also pointing out the character of each, he proceeded to inform them that many of the metals were found in veins in the rocks belonging to the formation they had just been considering; and the richest mines in Cornwall, where copper and tin ores were obtained, were in the primary clay-slate resting on granite; also the mine of Valenciana, at one time the richest in Mexico, where gold and silver were obtained, traversed the clay-slate and porphyry.

3d Ser. - 1843. III.

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Before proceeding to the transition series of rocks, he gave the young men an opportunity for making any observation they thought proper on the subject they had been hearing.

Bauldy Black was the first man that made any remarks. He said that he had listened wi' a' the attention he was able to give, and he thought he understood the subject as far as he had gane, for he once had some dealings wi' stanes. When he was a laddie on the farm o' Rashenbrae, mony a cart-load had he broken to fill drains wi’; but he never had heard so much said about rocks and stones before, nor did he ken that they had sae mony braw names before. “What ye ca' granite, we used to ca' it a ringer; and mica was sheep's siller; and quartz was liverwhin, and chucky stanes. But, Watty, is that no the diamond that is found in slates which you name pyrites? When I was herding, often hae I broken the slates for them; and large anes were sometimes found in a kind of slaty whinstone." Walter told him that the true diamond was quite a different substance altogether; that it was found in Bengal and the Island of Borneo, and also in Brazil and other places; and that it was found to be crystalline charcoal, while those yellow bodies that were obtained from roofing slate were composed chiefly of iron and sulphur. But it would appear that every country must have its diamonds, and almost every formation is sought for them; the Scotch seek for them in the primary formation, and the English in the gravelly hills of Bagshot Heath.

“ But what kind of a stane is that,” said Bauldy, “that ye have amang your specimens of primary rocks? I think I hae seen something like it sometimes turned up by the plough, and a hard heavy lump it is; there's nae braken o't; ye may maist as weel thump awa at a yetlin bullet; and I ance saw a sma' bit of it draw the needle of a compass to it, and make it spin round like Jenny Birril's wheel o' fortune on the end o' an auld herrin barrel at Broxbrae fair.”—“ That is magnetic iron-stone,” said Walter; “ and it is frequently found in primary mountains. It is also found in the Shetlands, and many parts of Germany and Sweden.”—“ And how had it found its way to the Rashenbrae?” said Bauldy.-" That is a subject which we will not enter upon at present,” said Walter; “but, perhaps, we will be able to give you information on that point when we are farther advanced in geology.”

West Plean, December 10. 1824.

In a

ART. JII. Bicton Gardens, their Culture and Management.

Series of Letters to the Conductor. By James Barnes, Gardener to the Right Honourable Lady Rolle.

(Continued from p. 52.) LETTER X. The Rockery. The American Garden. I will now, according to my promise, give you a short description, and the circumference of a few of the finest specimens of trees and shrubs in the American Garden and Rockery. The Rockery is covered with a collection of plants far too great for me to enumerate at present. Amongst them are fine specimens of many kinds of ferns, berberis, and ribes, of Cunninghàmia sinensis, &c. There is a constant supply of water coming out of the top of a pyramid of rocks in the centre of the rockwork, and trickling down the sides of it, thus forming a “weeping pillar;" and there are pipes and stopcocks in various parts the Rockery, so that you

have merely to turn them, to water the whole of it at once.

The American Garden, adjoining the Rockery, has a lovely stream of clear water running through it, over a bed of the beautiful round pebbles for which our sea-coast is celebrated. In this stream you see trout of different sizes enjoying themselves unmolested. This is the most delightful part of the garden from April to July, with its rich collection of the rarest rhododendrons, consisting of fine plants of the following, viz. : R. campanulatum, and the hybrid tig. grandiflorum varieties.

Lee's purple
Victòrice

daùricum altàicum
Cunninghamiànum

atrovirens nepalense

punctatum Glennyanum

myrtifolium venustum

chrysanthum strictum

caucásicum arboreum

pulcherrimum roseum

Nobleànum rubicundum

Russellianum álbum

prunifolium Webbianum

Rollissoni acutifolium

Smith supérbum

magnoliafolium coccineum

máximum grandiflòrum altaclerense

mirábile prínceps

catawbiense macránthum

spléndens tigrinum

fràgrans, and many others. Clumps of the richest and handsomest Ghent and other azaleas.

Likewise clumps or beds of Andrómeda, Lyònia, large plants of Leucothoe floribunda ; arbutus of sorts, pernettyas, clethras;

kalmias, noble clumps; ledums, vacciniums; cistuses, many varieties; helianthemums, all of these in fine clumps, of which it would fill a large book to give the names of all the varieties; Viburnum O'pulus rosea ; Stuartia marylandica, syn. Malachodendron marylándicum.

Height. Circumf. Name.

Ft. In. Ft. In. Acàcia dealbàta 20 0 38 0 Cércis canadensis 6 0 22 0

Siliquastrum 10 0 40 0 O‘lea europæ'a

yar. buxifolia

5 6 10 0 Cedronélla triphylla 120 Othónna crassifòlia - 10 0 Ozothamnus rosmarinifolius

10 0 Coronilla glauca 10 0 Ceanothus azùreus 13 0 The five last named

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Height. Circumf. Name.

Ft. In. | Ft. In. Cratæ'gus Douglàsü

12 0 42 0 macracantha

10

0 38 0 Crús-galli ovalifòlia 11 0 19 0

ovalifolia 14 0 42 0 obtusifolia 11 0 35 0 salicifolia

5 6 56 0 spléndens 14 0 40 0 punctata

13 0 39 0. orientalis

10 0 48 0 sanguínea 14 0 48 0 tanacetifolia

18 0 tanacetifolia 11 0 21 0 pyrifolia (edulis Lod. Cat.)

10 0 14 0 pyrifolia

12 0 40 0 glandulosa

7 018 0 apiifolia

10 0 39 0 coccinea

12 6 38 0 prunifolia

11 0 32 0 Pyracanthæfòlia 8 0 nìgra

16 0 27 0 lobàta

15 0 29 0 cordata

17 0 Oxyacántha me

lanocarpa eriocarpa laciniata

obtusàta parvifòlia mexicàna andmany others. Méspilus grandiflora 14 0 40 0 Photínia serrulata

(Cratæ gus glabra
Lod.) -

15 0 Gleditschia hórrida - 12 0 24 0 Amelánchier Botry

àpium Ligustrum chinense Amygdalus nàna Laurus Benzoin Acer créticum Elæágnus hortensis latifolia

Salisburia adiantifolia

10 0 Calycanthus Aóridus

lævigatus large C'ýtisus sessilifolius - 8 0 18 0 Bérberis asiática 16 039 0

Large plants of
Magnòlia acuminata 11 0 18 0

obovata
grandifòra

exoniensis
latifolia
angustifolia

lanceolata
macrophylla
tripétala
fuscata
pyramidata
auriculata
conspicua

Soulangiana 10 0 27 0 purpurea glauca

Thomsoniana 10 6 24 0 gracilis

cordàta A'bies Smithiana

canadensis Pàvia discolor U lex europæ'a flòre

15 036 0 Andrómeda acuminata

6 0 38 0 Chimonánthus frà. grans

6 0 20 0

plèno Cotoneaster micro- 5 0 18 0 phylla

14 0 24 0 Ailántus glandulosa

All the magnolias are good plants. Several varieties of escallonias, myrtles, daphnes, fine specimens of Andrómeda floribúnda, and many other fine and rare plants. A very lofty tree of Pópulus (álba var.) canéscens: the trunk, at 4 ft. from the ground, is 22 ft. 6 in. in circumference; and it is 42 ft. to the first branch, and then about 54 ft. above the first branch; therefore, the whole height is about 96 ft. The large beech tree in the flower-garden you took great notice of, and wished for the dimensions. The trunk, 4 ft. from the ground, is 12 ft. 6 in. in circumference, clear trunk, 38 ft. to the first branch; the tree altogether is about 78 ft. high. There was another beech tree exactly similar to the one I have described, which stood in the corresponding situation in the flower-garden, but was blown down about four years ago, and in its fall did much damage to the Maltese vases, &c.

Bicton Gardens, Oct. 22. 1842.

LETTER XI. The Trees in the Park. The Lake, and the Aquatic Birds. I will now give you the dimensions of a few of the noble trees that are growing in Bicton Park. Taking them altogether, I think I never saw so fine a lot of trees growing on the same space of ground. Some of the brave old oaks measure, at 4 ft. from the ground, 17 ft. to 18 ft. in circumference, and many of them spread their branches round to an immense distance. Several elms, about the same size in circumference, from 86 ft. to 100 ft. high. Remarkably fine beeches from 84 ft. to 96 ft. high; at 4 ft. from the ground, measuring from 13 ft. to 19 ft. in circumference. A good specimen of a Lucombe oak, 68 ft. high, the circumference of which is 8 ft. 6 in. The largest ash I ever saw, measuring 85 ft. high, 12 ft. in circumference, and going up in a straight line 30 ft. to the first branch. There are many fine specimens of chestnuts, limes, &c.; indeed, the trees of all kinds thrive very well here.

There is in the park a beautiful lake with islands, on which is a fine collection of black and white swans, and all kinds of aquatic birds and fowls; and in the winter it is covered with wild fowls of all sorts, which are never permitted to be shot.

Bicton Gardens, Oct. 29. 1842.

ART. IV. On Bottom Heat. By R. ERRINGTON. The subject of bottom heat has been much canvassed of late, but still it is a thing of indefinite character, and not, in my opinion, appreciated according to its merits. Dr. Lindley, in his excellent work, The Theory of Horticulture, has,

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