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 of 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."

66

West Plean, December 10. 1824.

ART. III.

In a

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 Cunninghamia 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 of 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. :—

Clumps of the richest and handsomest Ghent and other azaleas.

Likewise clumps or beds of Andrómeda, Lyònia, large plants of Leucóthoe floribúnda; 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 Opulus ròsea; Stuártia marylandica, syn. Malachodéndron marylandicum.

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 Populus (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 85ft. 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,

in a pointed and philosophical manner, endeavoured to draw attention to the subject. However, we want data to proceed upon; the vegetation year, or active period, is not confined by Nature to any given months, but moves by periodical fits. Those fits (a clumsy term, I confess,) are dependent chiefly on the relation that the bottom heat bears to that of the atmosphere.

I am of opinion that the average bottom heat of certain periods is much more in advance of the average of the atmosphere, at the same period, than is commonly imagined. I know it is common to say that the average bottom heat of the year is about 2 or 3 degrees in advance of the average atmospheric temperature; but this, if correct, proves nothing, except that bottom heat is one of Nature's established principles.

To obtain the data requisite, the year should be divided into natural periods : one of these is obviously the rest period; a second points itself out as the excitable period; and a third as the perfecting or accumulating period. Now, it is not proper, I conceive, to plunge a thermometer 1 or 2 feet deep to ascertain how vegetation is influenced by bottom heat, seeing that the chief and most efficient volume of roots lies probably within from 6 in. to 9 in. of the surface. The radiation, too, from the surface may also be taken into consideration; as the accumulation of heat by the end of August must be very considerable, especially within 3 in. of the surface.

The time was when bottom heat was only deemed essential for pines and cucumbers; but now few processes of any importance are conducted under glass without it.

Many complain that they cannot get their greenhouse and conservatory as gay through the months of December, January, and February, as they could wish; and I do not wonder at it. If plants in a somewhat dormant state are to be subjected to a higher temperature all of a sudden, without activity of root, what can be expected but abortions?

I am led to make these remarks in consequence of observing the effect of bottom heat in flower-forcing in general, more especially Dutch bulbs. Mine have been unusually early and good; and I adopt a practice which deserves to be more generally known. My hyacinths, narcissuses, &c., are potted at the usual time and in the usual way, and immediately plunged over head in old tan. This so far is every body's plan; but about the end of October I take them up, and prepare a bottom heat of from 75° to 80° of dung and leaves, between the bricked asparagus pits, and place the pots thereon, covering them as before with old tan. When this heat declines, I prepare the next pit in like way, and remove them into it; keeping them, in fact, in a similar bottom heat constantly. By these means I get my root in advance of the bud; for, this season, having paid close attention to their movements, I found the pots were full of roots, and well coiled round the bottoms of the pots, before the buds were an inch long. This I conceive to be a point of high importance; for on removing them from the asparagus pits to a forcing-pit of dung and leaves, where the bottom heat was 80°, and the top heat averaging 65°, the buds came up like magic, and were in bloom in a surprisingly short period. The same principle applies to nearly all of what are termed forcing flowers; not excepting strawberries, which, in my opinion, would be much benefited by such a process. However, I have not yet proved this with strawberries, although I have several experiments in progress, bearing on the subject of bottom heat, which I shall probably make known as soon as completed.

When the various flowers possessing capabilities for forcing are taken into consideration, we may fairly conclude that our conservatories and greenhouses ought to be as gay in the month of January as during any part of summer, and so, in fact, have mine been; for I have had abundance of camellias constantly from the first of November (some thousands of blossoms), violets, lilies, azaleas, bulbs, justicias, lilacs, eranthemums, and scarlet geraniums, in great profusion, now, indeed, a complete blaze of colour.

Oulton Park, near Tarporley, Jan. 20. 1843.