Ar one of the meetings of the Chemical Section of the British Association for the advancement of Science, the preparation of a Report on Organic Chemistry was assigned to Dr. Justus Liebig, Professor of Chemistry in the University of Giessen. This Report has been edited by Dr. Lyon Playfair, and recently published under the title of "Organic Che mistry, in its applications to Agriculture and Physiology." From this work, which is one of the most profound and useful contributions to science, we propose to select a few subjects capable of being presented to the reader in a popular form.

IT has long been known to the agriculturist that the growth of annual plants is impeded, and the produce rendered less abundant, by cultivating them during successive years on the same soil, and that, notwithstanding the loss of time, a larger quantity of grain is obtained when a field is allowed to remain uncultivated for a year. During this interval of repose, the soil, in a great measure, regains its fertility.

Experience has also led to the observation that certain plants, such as peas, clover, and flax, flourish on the same soil only after a lapse of years; whilst others, such as hemp, tobacco, rye, and oats, may be cultivated in close succession. It has been also found that several of these plants improve the soil, whilst others, and these are the most numerous, impoverish or exhaust it. Fallow turnips, cabbage, beet, spelt, summer and winter barley, rye, and oats, are supposed greatly to impoverish the soil; whilst wheat, hops, madder, late turnips, hemp, poppies, teasel, flax, weld, and licorice, are supposed to exhaust it entirely.

From the earliest times manure has been employed to increase the fertility of soils; and experience has proved that manures restore certain constituents to the soil, which have been removed by the plants grown upon it; but it has been observed that crops are not always abundant in proportion to the quantity of manure employed, even, although it may have been of the most powerful kind: that the produce of many plants diminishes in spite of the apparent replacement of the substances removed from the soil by manure, when they are cultivated on the same field for several years in succession.

It has been remarked, on the other hand, that a field which has become unfitted for a certain kind of plants was not on that account unsuited for another; and, upon this observation, a system of agriculture has been gradually formed, the chief object of which, is to obtain the greatest possible produce with the least expense of

manure.

It was deduced from the foregoing facts that plants require for their growth different constituents of soil, and it was very soon perceived that an alternation of the plants cultivated maintained the fertility of a soil, quite as well as leaving it at rest or fallow. It was evident, therefore, that all plants must give back to the soil in which they grow, different proportions of certain substances, which are capable of being used as food by a succeeding generation.

Many explanations have been offered respecting the cause of the favourable effects of the alternation of crops; but the theory of De Candolle is the one which has received the greatest share of attention.

This distinguished botanist supposes that the roots of plants imbibe soluble matter of every kind from the soil, and thus necessarily absorb a number of substances which are not adapted to the purposes of nutrition, and must subsequently be expelled by the roots, and returned to the soil as excrements. Now, as excrements cannot be assimilated by the plant which ejected them, the more of these matters which the soil contains, the more unfertile must it be for plants of the same species. These excrementitious matters may, however, still be capable of assimilation by another kind of plants, which would

thus remove them from the soil, and render it again fertile for the first. And, if the plants last grown also. expel substances from their roots, which can be appropriated as food by the former, they will improve the soil in two ways.

This view of the subject is countenanced by many well-known facts. Every gardener knows that a fruittree will not grow on the same spot, where another of the same species has stood; at least not till after a lapse of several years. Before new vine-stocks are planted in a vineyard from which the old have been rooted out, other plants are cultivated on the soil for several years. It has also been remarked, that several plants thrive best when growing beside one another; and, on the contrary, that others mutually prevent each other's growth. Whence it was concluded, that the beneficial influence in the former case depended on a natural interchange of nutriment between the plants, and the injurious one in the latter on a poisonous action of the excrements of each on the other respectively.

But the theory of M. De Candolle has been confirmed in a satisfactory manner by a series of admirable experi ments by M. Macaire which we will briefly detail.

The roots of the Chondrilla muralis were carefully cleaned and immersed in filtered rain water: the plant continued to flourish, and put forth its blossoms, and st the end of eight days the water was of a yellowish colour, indicating to the smell and taste the presence of a bitter narcotic substance, similar to that of opiuma result which was further confirmed by using chemical tests, and by a reddish-brown residuum which remained after evaporating the water. It was ascertained that neither the roots nor stems of the same plants, when com pletely detached and placed in water could produce this effect, which seems to be the result of an exudation from the roots, necessary to the health of the plant. By comparing the results of various experiments on the quantity of matter thrown off by the roots of the French bean, by night and by day, it was found to be much more considerable by night, an effect which it is natural to refer to the interruption of the action of the leaves when deprived of light, and when the corresponding absorption by the roots is also suspended. This was confirmed by the result of some experiments made on the same plants by placing them during the day in a darkened room, when the excretion from the roots was found to be much increased; but, even when exposed to the light, there is always some exudation, though in small quantity, going on from the roots.

By this excretory process plants are enabled to get rid of any noxious matters which they may have absorbed from the soil. This was proved by experiments on several plants, among which was the common cabbage. The root of the cabbage was washed clean, and the fibres separated into two bunches, one of which was immersed in a weak solution of acetate of lead, and the other bunch in pure water, contained in a separate vessel. After a few days, during which the plants vegetated tolerably well, an appreciable quantity of acetate of lead was found in the vessel which contained at first only pure water. In order to prove that the poison was actually absorbed into the body of the plant the experi ment was varied: the plant was first allowed to remain with its roots immersed in a solution of acetate of lead: it was then removed and carefully washed, in order to get rid of all traces of the solution from the surface of the roots, after which it was placed in a vessel containing pure water, which in two days' time became contami nated with acetate of lead. Similar results were obtained when lime-water and a solution of common salt were substituted for the acetate of lead.

M. Macaire also found that the water in which certain plants had been kept was injurious to other plants of the same species, while it produced decidedly beneficial effects on plants of a different kind.

When substances which cannot from their nature be employed in the nutrition of a plant exist in the matter absorbed by its roots they must be again returned to the soil as excrements, which, however, may be serviceable, or even indispensable, to the existence of several other plants. Substances, however, that are formed by the vegetable organs during the process of nutrition, which

some plants (as in the grasses) in the form of silicates; in others in the form of tartrates, citrates, acetates, or oxalates. Some species of plants require phosphate of lime, or phosphate of magnesia, and several do not thrive without carbonate of lime.

The matter thrown off by the roots of plants as excrements, undergoes during autumn and winter a useful change from the action of air and water: its putrefaction, and at length by continued contact with the air, which tillage is the means of procuring, its decay, are effected; and at the commencement of spring it has become converted, either in whole or in part, into a substance which supplies the place of humus*, by being a constant source of carbonic acid.

The quickness with which this decay of the excrements of plants proceeds, depends on the composition of the soil, and on its greater or less porosity. It will take place very quickly in a calcareous soil; but it requires a longer time in heavy soils, consisting of loam or clay.

The same plants can be cultivated with advantage on one soil after the second year, but in others not until the fifth or ninth, merely on account of the change and destruction of the excrements, which have an injurious influ ence on the plants, being completed in the one, in the second year; in the others not until the fifth or ninth.

In some neighbourhoods clover will not thrive till the sixth year; in others not till the twelfth; flax in the second or third year. All this depends on the chemical nature of the soil; for it has been found by experience, that in those districts where the intervals at which the same plants can be cultivated with advantage are very long, the time cannot be shortened even by the use of the most powerful manures. The destruction of the peculiar excrements of one crop must have taken place before a new crop can be produced.

Flax, peas, clover, and even potatoes, are plants, the excrements of which in clayey soils require the longest time for their conversion into humus; but the use of alkalies and burnt lime, or even small quantities of wood ashes, (which have not been wetted so as to remove the alkali contained in them,) must enable a soil to permit the cultivation of the same plants in much less time.

A soil lying fallow owes its earlier fertility, in part, to the destruction or conversion into humus of the excrements contained in it, which is effected during the fallow season, at the same time that the land is exposed to a further disintegration. In the soils in the neighbourhood of the Rhine and Nile, which contain much potash, and where crops can be obtained in close succession from the same field, the .allowing of the land is superseded by the inundation. The artificial irrigation of meadows effects the same purpose. It is because the water of rivers and streams contains oxygen in solution, that it effects the most complete and rapid putrefaction of the excrements contained in the soil which it penetrates, and in which it is continually renewed. If it was the water alone which produced this effect, marshy meadows should

be the most fertile.

A fertile soil ought to afford to a plant all the inorganic bodies necessary to its existence in sufficient quantity and in such condition as allows their absorption. All plants require alkalies, and these are contained in Woody fibre, in a state of decay, is called humus, and is the principal constituent in mould. Humus acts in the same manner in a soil perme able to air as in the air itself; it is a continued source of carbonic acid, which it emits very slowly. An atmosphere of carbonic acid formed at the expense of the oxygen of the air surrounds every particle of decaying humus, The cultivation of land by tilling and loosening the soil, causes a free and unobstructed access of air. An atmosphere of carbonic acid is therefore contained in every fertile soil, and is the first and most important food for the young plants which grow in it.

The rural ditties were not mute,

Tempered to the oaten flute,

Rough satyrs danced, and fauns with cloven heel
From the glad sound would not be absent long,

And old Damætas loved to hear our song.--MILTON.

AMONG the musical instruments familiarly known to us at the present day, there is one which, though it has acquired a sort of a character for vulgarity, is one of the most ancient of all. We allude to the Mouth-organ, known to classical readers by the names Syrinx, and Fistula Panis, or Pan's Pipes.

The formation and the mode of playing musical instruments among the ancients have formed the subject of considerable research; great difficulty being experienced in knowing the proper interpretation or translation to be given to certain terms used by the classical writers. The first attempt at a wind instrument seems to have been the employment of the shell of some particular fish, or the horn of a quadruped. To this probably succeeded the use of the Arena, or single oaten stalk; the Calamus, or single reed; and the Syrinx or Fistula, a number of reeds of different sizes, ranged side by side, each one stopped at the lower end. It was the opinion of Dr. Burney, that such simple instruments as these, in which each pipe is employed to yield but one note, preceded the employment of those which were provided with foramina, or holes, and which, by stopping one or more of these holes with the fingers, could be made to yield several notes. When this latter method became known, a great advance in the musical art resulted; and the artificers gradually attained the skill to make such instruments of box-tree, laurel-wood, brass. silver, and even gold.

Flutes or pipes, called Tibiæ, were much used in the theatrical exhibitions of the ancients, some of them approaching nearly to the form of a shepherd's pipe, as represented in old pictures, and indeed all of thein bearing more resemblance to a flageolet than to a modern flute. But with regard to the instrument now called a mouth-organ, it does not appear to have been similarly employed. It is a circumstance not a little remarkable, that the god Pan is almost invariably represented as playing on this instrument; a fact which, whatever may have been its source, is strongly indicative of the familiar use of such an instrument among the early Greeks. In some of the pictures wherein Pan is introduced, the syrinx on which he appears to be playing, is composed of tubes or pipes having a square sectional area; while in others the pipes are of cylindrical form. In the cut at the end of this article, the pipes are six in number, and of a square form. This representation is taken from an ancient basso-relievo of Greek sculpture, in the Giustiniani Palace at Rome, the sculpture pourtraying the nursing of Jupiter by Amalthea. Pan is holding the syrinx in his left hand, while in his right he grasps a horn, resembling the shawm, represented upon the Arch of Titus, among the instruments supposed to have been copied from those brought by this emperor from Jerusalem.

A French writer of the last century relates his having seen at Rome, on a monument in the Farnese Palace, a syrinx with eleven pipes; the first five being of equal lengths, and consequently producing notes of the same pitch; with six others of equal diameter, but of different lengths from the first five. "I confess," says he, "that

I am unable to conceive the use of the five first reeds or pipes of the same length for no two of them could be made to sound at once. Is it not possible that these

Magazine.

THE town of Nuremberg, or Nürnberg, in Bavaria, though fallen from its ancient wealth and consequence, and become, in a commercial sense, a dull and unattractive spot, will nevertheless be pleasing to the traveller of taste, and will fully repay the attention he may be induced to bestow on its examination. In former days it was one of the most flourishing towns included in the Hanseatic league, and was reckoned among the most wealthy of the free Imperial cities. It was the residence of emperors, the seat of diets, and, before the trade with the East Indies took a new direction, the focus of commerce between Asia and Europe. Nor were these its only advantages: the manufactures of Nuremberg were long and justly celebrated, and brought a large accession of wealth to the town. Various mathematical and musical instruments were invented, and the first pocket-watches made in that town. The manufacture of these articles, as well as of hardware of all kinds, and toys of brass and wood, caused Nuremberg to be highly celebrated. The trade in such wares is still very considerable, and, owing to the cheapness of the toys in particular, half the children in Europe are supplied with playthings, called Dutch toys, from that source. These toys are chiefly made by the peasants of the Thuringian forest, who employ themselves and their families on such labours during the winter, and by their simple and frugal habits, are able to produce them at a surprisingly low price. For the sale of Nuremberg wares an annual fair is held, at which much business is VOL. XIX.

transacted. Yet, compared with its ancient traffic-so extensive as to give rise to the proverb,

Nuremberg's hand

Goes through every land,→ the present trade of Nuremberg may be called trifling, as the condition of the city is also greatly altered.

The outward aspect of Nuremberg has not partaken much of the decay which has fallen on its commercial interests, and it is in the appearance of the city, as it stands surrounded by feudal walls and turrets, and inclosed within arched gates, with massive cylindrical watch-towers, that the traveller may recognise its ancient grandeur and strength; while, as he examines the quaint buildings of the city, and wanders through its irregular streets, he may fancy himself carried back to a distant century. Most of its churches are in a state of beautiful preservation, and have escaped in a manner that seems almost miraculous, the storm of regular warfare, and the outbreaks of mistaken zeal. The principles of the Reformation were early embraced by the inhabitants of Nuremberg; but the churches were not, as in too many other instances, despoiled of their architectural embellishments. The private dwellings, many of them of a palace-like extent, and built of stone, are likewise in excellent preservation, and are in some instances still inhabited by the families whose forefathers originally constructed them.

Nuremberg is celebrated as the birth-place of Albert Dürer, called the Raphael of Germany; of the famous

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