is improper and insufficient, when applied to mean the elaborated sap, proper juice, or nutritive fluid of plants, which they have too generally been. It is clear, also, if we adopt the idea, that the nutritive fluids, capable of serving the general purposes of the plant, circulate through such capillary vessels, then there must be other similar vessels in these plants containing those nutritive fluids, which may hereafter be found to be the case. The nutritive fluid must contain carbon, hydrogen, and oxygen, in something near the proportions required to form the system in general; to which mucilage seems to be the nearest approximation of any of the organisable or proximate products. It must also contain nitrogen, indispensable in the formation of all new matter, besides being assimilated by many of the organs; this may be in the state of fibrin or gluten, so easily separated from the vegetable juices, or in the state of proteine, the basis of fibrin or gluten, albumen, and caseine, which differ only in their saline earthy ingredients. The nutritive fluid must also contain the saline earthy ingredients required for so many of the organic products. The cambium, the main product of the elaborated sap, is principally composed of mucilage. The mucilaginous juices have not been so much submitted to analysis as the milky juices; but the analysis of mucilage of lintseed, given Vegetable Chemistry, p. 674., shows their fitness for the purposes of general nutrition. It contains, besides 7.11 per cent of ashes of saline matter, the following proportions of organic, viz. :-

The excess of hydrogen and oxygen above carbon is owing to the mucilage containing 10 per cent of water, which is probably contained in tissue in a free state. Müller says all the animal tissues contain of water in a free state, and, if this be pressed out, they cannot live. Seeds also contain free water, and, if this be dried up, they die. Water seems necessary to preserve the capability of living in the tissue.

From juices of this description the general products of the system might be formed; and if mucilaginous juices similar to the above are found by subsequent observation to circulate in masses of capillary vessels similar to the laticiferous, and in sufficient quantity to furnish a channel for the general current, we may then adopt the opinion that the general circulation passes through vessels of this description. If not, we must resort to the old opinion, that such products are peculiar secretions circulating in peculiar vessels, and not the general channel of circulation as supposed by Dr. Carpenter.

Besides the assistance of gravitation, vibration, contractility,

and attraction and repulsion, in the descent and course of the elaborated sap down the bark and along the medullary rays, and perhaps also in masses of smaller vessels, to furnish the nutriment needed for the different parts of the system, the power of endosmose is an assistant in the circulation, in such as the bursting of anthers, capsules, &c., and generally wherever thinner fluids are attracted to the more dense. If it is correct, as stated, that endosmose often takes place from thicker to thinner fluids, it may be found more general than supposed through the circulation. If due to electricity, it may also be found that the same electricity which produces the elective affinity of the physical causes, may likewise be concerned, by acting on the excitability of the membrane, in causing the much greater power of endosmose through organised membrane, than through porous inorganic septa, which is found to take place.

"The

In Chap. VII., On Interstitial Absorption, he says:circulating system not only serves to convey to the remoter parts of the organism the materials required for the nutrition of their tissues, but in the lower animals returns to the central reservoir the portion which has not been so employed, and those particles of the solid structure which, from tendency to decompose or other causes, are unfit to be retained in it. In the Vertebrata, which possess a special set of vessels for the absorption of chyle from the intestines, allowing the portion not absorbed to pass on and be rejected, we find also a system of tubes ramifying through every part, to which the function of absorption seems more particularly delegated. The lymphatics, as they are termed, are distributed through almost every tissue in the body; they are especially abundant beneath the skin, forming a close network so universally diffused, that, if successfully injected, it is scarcely possible to find a spot not traversed by them. They commence, like the lacteals, without open extremities, deriving their contents by imbibition or endosmose from the surrounding tissue; they unite into large trunks, and by these the fluid taken up by the absorbent extremities is conveyed to the principal veins. The cause of motion in the lymphatics, besides the endosmose one of absorption, is probably peristaltic, by which their fluids are propelled forward, the reflux being prevented by the valves with which they are plentifully supplied. The veins themselves, in many cases, participate in the function of absorption more actively than the lymphatics." The lymph taken up in this way is said to be nearly identical with the fluid portion of the blood, or serum, containing the portion called serosity, supposed to consist partly of effete particles, furnishing the matter excreted by the kidneys, &c. The waste of the system is supposed to be taken up by these means and conveyed into the circulation, where part of the car

bon is oxidised and given off in respiration; part of the carbon and hydrogen of the waste, and the non-azotised portions of the food, being separated by the liver to form bile, which, after assisting in forming the chyme into chyle, is partly excreted with the matter of the food rejected (Liebig says all the waste of the body and non-azotised parts of the food pass through the liver). The nitrogen and saline earthy substances of the waste are carried off and excreted by the kidneys. These matters, belonging to Animal Physiology, are foreign to the objects of our present essay, were it not for the presumption they afford, that something of the kind may yet be found to exist in plants.

(To be continued.)

ART. II. Dinbur Castle, its Gardens and its Gardeners. By Peter MACKENZIE,

(Continued from p. 416.)

In the explanatory introduction to the natural arrangement of your Hortus Britannicus, you have given directions how gardeners may know the quantity of ground required in the formation of arboretums or herbaceous grounds; and, after giving directions how to find the square root of all the smaller squares which would contain all the hardy herbaceous plants of a tribe or order, you say that "every gardener knows, or ought to know, how to modify this square to a parallelogram, a triangle, or a circle, of the same capacity." I believe that there are too many gardeners deficient of much knowledge which they ought to be in possession of; and, perhaps, among the various branches of the tree of knowledge, that of practical geometry is not cultivated to the extent which it ought to be. There are some to be found who would have some difficulty in telling the number of square feet or square yards that may be in their onion beds, although they may be in squares or parallelograms. Perhaps geometry was more studied by gardeners and foresters a hundred and twenty years ago than it is at the present day. Although many of the young men employed in gardens may have had a tolerable education before they commenced working, there are few of them who have studied the first properties of the circle; or, a circle being given, to inscribe in it, or describe about it, an equilateral triangle, a square, a regular pentagon, or a regular pentadecagon: neither have they studied the many useful things that are performed by means of the triangle, or made themselves familiar with the different measuring units employed in the various subjects of measurement. Perhaps it may be of little use to them to be acquainted with the measuring unit of the astronomer, or the square mile of the geographer; but it will

be of great use to them to be acquainted with the measuring units of the land-surveyor, the carpenter, the glazier, the mason, and bricklayer. It sometimes happens that gardeners are required to measure artificer's work, and they sometimes look awkward enough when they cannot do it. It was not a bad thing in some of the old works on gardening, to have a chapter giving directions how to measure, divide, and lay out land: for, although there are many books on the subject to be had, yet many journeymen gardeners may be without them; and, though it may be a simple thing to measure a square, a parallelogram, or a triangle, or to raise a perpendicular, or draw an oval figure, yet there are not a few who may be looked upon as good gardeners, who would perhaps find some difficulty in doing them properly, when it was required of them to do them. I speak from what I have seen in royal gardens and downwards. There are few gardeners but have some works on gardening, and, if a few simple directions were given how to measure geometrical figures in some part of the book, it might assist them greatly at times. But, towards acquiring a knowledge of the superficial or solid contents of bodies, nothing is equal to the doing of the thing; an hour's practice is worth many hours' study with books.

The gardener of Dinbur Castle was well aware of the advantages that were gained by active perseverance after knowledge, and he wished to impart to his men such information as would be useful to them; he was destitute of that narrow-minded imbecility which will not communicate with other minds which are reckoned beneath him; he believed that the more useful knowledge was disseminated, the probability would be greater of having physical obscurities dispelled, and, though one failed in accomplishing the object of his desire, others might be successful in discovering some of the inexhaustible fountains of knowledge which a bountiful Creator has placed within the reach of finite minds to open.

One evening in summer when the labours of the day were past, when the lads in the bothy had partaken of their evening meal, and had rested themselves a little, their master came among them with his measuring-chain and cross-staff, picket staves, and arrows. He soon told them that the object of his visit was to give them a few lessons in land-surveying, and, though it was upon their own time, he hoped they would give him their attendance for a few hours, for he trusted it would be to their own advantage in after life, when they would have charges of their own. All showed their readiness to attend their master. They went into a pasture field, where they were to commence operations, and, although some of them knew a little of land-surveying already, yet he thought it would be as well to give them a few instructions relating to the geometrical figures in which pieces.

of land are commonly found to be; so, instead of giving his lessons on paper, which is a common practice, he marked off with his picket staves a large square, and showed that by multiplying the base side by the perpendicular, the number of square links, or feet, or yards, would be found. After Bauldy had understood how to find the contents of a square, he next formed a parallelogram, and showed that the area is found by multiplying the length by the breadth. He next formed the rhombus, and directed them to multiply the base by the perpendicular height, and they would find the area: he also showed them the difference between the rhombus, and the rhomboides from the rhombus. He proceeded to the triangle, and showed them various ways of finding the area; first, by multiplying the base by a perpendicular demitted from the opposite angle, half the product is the area; or, by multiplying the base by half of the perpendicular, or the perpendicular by half of the base. After the triangle he formed the trapezium, and, dividing it into two equal parts by a diagonal line, and demitting perpendiculars from the other angles and multiplying the diagonals by the sum of the two perpendiculars, showed them that half the product is equal to the area. Next in order he described the trapezoid, the regular polygon, the circle, circular ring, segment of a circle, and the ellipse.

Having gone over the various forms in which the different parts of our earth are commonly found, or a combination of them, he found that he had not time to measure the fields which he intended. The sun was descending towards the highland mountains, and the long shadows of the evening were gathering around them, so it was agreed that they should draw their operations to a close, and resume them again at an early opportunity. When they were leaving the field the attention of Bauldy appeared to be fixed upon a beautiful Lombardy poplar that was growing near the place where they were. At last he said, "Weel master, I hae aften wondered what the hight o' that tree may be, but I dinna ken how to reach the top o't." ،، But you may soon know the height of it, Archibald, without going to the top of it," replied his master. "The sun has not yet set,

and the shadow of the tree is very distinctly seen upon the field, so that the length of the tree's shadow may be easily known." He knew the length of one of his picket staves, and measured its shadow and also the shadow of the Lombardy poplar; he applied the rule of three to the three given numbers, and in a few minutes he told Bauldy that the height of the tree was about 70 ft. Bauldy thanked his master for the information he had given him, and added that it was "a braw thing to hae lair, for it made them that made a gude use o't like a different set o' folk althegither.” "I am glad to see you, Archibald,” said the master, "so desirous to obtain useful acquirements, and