length of the side of this square is 4 in. A diagonal line is drawn across from the angle c; and parallel to this line, a brass pendulum is suspended from a side pin. This pendulum has a curved limb or finger e attached anywhere near its middle; and the pendulum and curved limb are kept from flying off the board by two brass guards, which, however, admit the free action both of the pendulum and curved limb. At the extremity of the muzzle c, a sight is fixed, as in the barrel of a common fowling piece, to guide the eye; and the but-end of the instrument being applied to the shoulder, and the sight on the end of the barrel part directed to the top of the tree, the operator advances towards it or retires backwards till the point of the curved limb is visible above the line of the stock, as in the figure. The circumstance of the curved limb being visible above the barrel part of the instrument, proves to the operator that the plumb line rests on the diagonal line of the square, and consequently that the angle made by the eye of the operator with the top of the tree is 45°. The distance of the operator from the tree, and the height of his eye from the ground, being then added together, give the height of the tree; unless the ground should not be level, in which case allowance must be made, either by adding or subtracting, according as the ground may be lower where the operator stands than at the root of the tree, or the contrary. 48 This instrument, I believe, was invented by Mr. Cuthbertson, the head gardener at Studley Royal, who was my constant assistant in taking the measurements. It has occurred to me, that the same principle might be exemplified in a more portable instrument, and I have accordingly contrived fig. 48., which is only 12 in. long on the upper side. It is made of box, with a brass octant suspended from its centre, and loaded at the extremity, with a curved limb, as in fig. 48. It is unnecessary to describe the manner of using it, which is precisely the same as that of the preceding figure. London, May, 1840. ART. VI. On the Decay in growing Larch and Spruce Fir Trees. You have often taken notice of the decay in larch and spruce fir trees, commonly called the rot, and invited opinions as to its cause. As nothing satisfactory has been discovered on the subject, I venture my opinion, which is, that this decay proceeds from the too rapid growth of the trees when young, and from their very slow growth when aged. In confirmation of my opinion, I have sent you specimens from decayed, and also from healthy trees, taken from the trunks and from the roots. When larch and spruce firs are young, they grow often rapidly, and the wood formed at that period is very porous both in the trunk and roots. As the trees advance in age, the supply for their growth is less, from the soil being greatly exhausted, and often from the trees not having been thinned out in proper time. The outer case of wood then formed is less porous, and becomes in time too compact to admit air to the early formed wood within. This latter being of a coarse grain, the dry rot begins to infect it, in the same manner as it attacks wood which has been painted in a green state, the paint excluding the air from the inside wood. The specimen No. 1., taken from the root end of a decayed larch, is an example. The decay in the trees goes on more or less rapidly, according to the grain of the wood. It ascends the trunk and makes its way along the roots; at least those first formed which have become the conducting tubes to the trunk from the smaller roots and fibres. As the disease advances, the sap collected in the fibres passes with difficulty through the decayed conductors to the trunk, and the trees become sickly, although the small roots and fibres where the sap accumulates be healthy. This will be evident in the root specimen No. 1., cut off 1 ft. from the bole of the tree. As farther proof that decay proceeds from too quick a growth, the trees that have grown beside decayed ones, but happened to grow slowly, have been found sound; and it may often be observed, in trees partly decayed, that it is the quick growths in the trunk that are rotten. Specimen No. 2. shows the former, and No. 3. the latter. Decay may, in some cases, have proceeded from other causes; when trees make unusually large growths, as in specimen No. 4., such wood cannot last long. In this specimen, however, the outside wood is of fine grain. The supposition, that the soil is the cause of rot, is in a great measure correct, if climate be taken in conjunction with soil. It is a common observation, that a tree has got down to a soil which it does not like. If the soil were in fault, the wood grown then would be bad, whereas in reality it is the best. The error lies in the supposition that the decay proceeds in age from soil and climate; but its foundation is actually laid in the youth of the tree. In proof of this, it is a known fact that trees grown in cold and barren situations are always sound. Their growths are small, and the wood in consequence is durable. The best larch, for instance, in Britain, is grown at Dunkeld. The Athole frigate was built of it, and has well proved its durability. Those grown among the rocks are the soundest. When they were planted, there was hardly soil enough to cover their roots, but their foliage annually falling and decaying in crevices of the rocks, formed sufficient soil for them; and the supply increases as they advance in age. Larch grow there as in their native Alps. To this it may be objected, that the oldest larches in Britain, viz. those at Dunkeld, grow in garden soil, as do other fine trees in various places, especially in North Britain. For instance, at Melville House, Fifeshire, there are or were some fine larch trees growing on good land; and at the Whim, Peeblesshire, there are fine healthy spruce firs on wet bog soil. As these trees must have made strong growths, they may appear to offer a direct contradiction to the above statement, namely, that overgrowth in youth and undergrowth in age combine to cause the rot. It must be considered, however, that the aged trees at Dunkeld were kept when young as green-house plants, and probably stunted, so that they formed small-grained wood at first. Though they made large growths afterwards, the trees grew apart from others, and were not robbed of their supplies, so that it is most probable that their outside growths are in the same proportion as those of the inside. The same will apply to the other two cases mentioned above; and, so far from their being at variance with my theory, it was from having observed them that I was led to its adoption. Still it may be alleged that trees grow thick together in their native forests, and yet produce the best wood. This is true, but it must be remembered that the trees are in their natural climate, which is much colder than ours, and, of course, make slow growths. Those made while the trees are young are often the smallest, reversing the growth of our climate, where the trees that have grown quickly when young, are often starved in their after growth. This is not the case in natural forests, where trees find abundant nourishment from the mass of decayed vegetable matter which falls from the trees, and is not swept away like that in artificial plantations. From the rot being more prevalent now than it was formerly, it has been supposed that the trees are of a different kind from those first planted. It has been said that they came from North America. This I do not believe; but, if it were true, it is not probable that they were natives of colder regions than those first planted here, and if so, they would not produce wood of coarser grain, or more likely to decay. If there are some varieties raised in this country from the original stock, they would be more likely to become naturalised here, and would perhaps stand better than the original trees; yet it is a wellknown fact that some of the progeny of the ancient trees have 1 been infected with the rot. The question then is, how comes it that the disease has been on the increase of late years? One thing to be considered is, that there have been more trees planted, especially larch trees, and less care has been taken of them, than formerly. The trees are often left thick together, to form cover for game, the soil in consequence soon becomes exhausted, and the thinning at last comes with a vengeance, but too late. Another question is, why fir trees die when they become hollow, whereas many other trees live to a great age as hollow as a drum? The case of the firs is, however, different from that of their hollow neighbours; their disease being internal, both in trunk and root, while other trees often grow hollow from some external injury to branch or trunk, which does not affect their roots, so that they often grow vigorously while their rind and bark continue sound. If I am wrong in the opinion that the rot proceeds from the external wood excluding the air from the heart or inside of the tree, at least there can be no doubt that the seeds of decay are first sown by too rapid growth; and little do planters think, when they admire the great progress of their young firs, that such rapid growth is but laying the sure foundation for trees rotten. at heart. Cossey Hall Gardens, April 1. 1840. ART. VII. On grafting the Acàcia. By JOHN BREWSTER, Gardener to Mrs. Wray. I HAVE often lamented to see the dwarf, delicate, but still beautiful, species of Acàcia struggling for life among their more hardy and robust brethren, and especially when the desirable object of placing them in a situation calculated to show their humble beauties to advantage, and impart to them a more hardy and robust constitution, is so easily obtained by grafting. This operation may be performed in almost any situation. Perhaps the best stock would be Acàcia affinis, owing to its rapid growth, and to its being hardier than any of the rest. I have known this species grown out of doors (from seed) to the height of 17 or 20 ft. in three years! What a magnificent object a tree 20 ft. high, grafted with perhaps fifteen or twenty species, including A. pulchella, A. diffùsa, A. cyclops, &c., would be! The great diversity of their splendid foliage, intermixed with their beautiful flowers, would form an object truly grand. By choosing a strong stock, and planting it out of doors in the early part of May, and then, as soon as it had taken root, grafting it, cutting it down to within a few eyes of each graft; or, if it can be conveniently done, inarching it, a fine tree would be formed in a very short time. The scions may be put on of almost any size, even a large plant. Smaller plants may be grafted or inarched either in the stove or green-house. The plants that are grafted out of doors I would recommend to be potted in the autumn, in order to give them a little protection in winter; again planting them out in spring; and by continuing this system for two or three years, the grafts will become fairly established, when they may be left out all winter, with a good covering of mats in frosty weather. If the above hints be thought worthy the attention of any of the numerous cultivators of this beautiful genus, I will yet hope to see the pendulous, dwarf, and delicate species attain the first place as ornamental plants, which they so richly merit, both in the green-house and pleasure-ground. Oakfield, Cheltenham, June 13. 1840. ART. VIII. Notice of a Plant of Cèreus grandiflòrus, at Eatington Park, Shipston on Stour. By W. HUTCHISON, Gardener to E. J. Shirley, Esq., M.P. I SEND you an account of a plant of Cèreus grandiflòrus now in flower in the pine-stove here. It is a mistaken notion, that the night-flowering cereus, as it is commonly called, only flowers at 12 o'clock at night, and is off before the following morning. The plant here covers a trellis on the back wall of the pine-stove 7 ft. by 6 ft. Yesterday evening, at 8 o'clock, there were fifteen flowers fully out at one time. It was one of the most magnificent sights imaginable. It filled the whole house with odour; indeed, so strongly is it scented, that you can smell it before you open the door of the house. It is rather singular that for three successive seasons the number of flowers has been the same, viz. 21. The soil used is very light sandy loam, if loam it can be called, as there is very little in it but sand. From August to February very little water is given; as the spring advances, it is given more freely. When the flower buds appear, water is given very plentifully, and the buds swell fast and expand in all their glory. Eatington Park, June 13. 1840. ART. IX. On the Causes of Canker in Fruit Trees. By JOHN JENNINGS. I BEG to offer a few remarks on the canker in fruit trees, but more particularly in the pear tree. I have been endeavouring to learn its cause, with a view to exterminate it if possible; and, from the observations I have made, I am led to conclude that it is |