of much importance to the agriculturist that he should not deceive himself respecting the causes which give the peculiar action to the sub

stances above-mentioned. It is known that they possess a favourable action on vegetation, and it fon is likewise certain that the cause of this is their containing a body which, independently of the influence exerted by its physical properties of

ange

velopment unless nitrogen is also afforded to it. A herb will be formed, but no grain; even sugar and starch may be produced, but no gluten.

But on the other hand, the supply of nitrogen in the form of ammonia will not suffice for the purposes of agriculture. Although ammonia is of the utmost importance for the vigorous growth of plants, it is not in itself sufficient for the production of vegetable caseine, fibrine, and albumen. These substances are not known in a free state, for they are always accompanied by alkalies, sulphates and phosphates. We must therefore

assume that without their co-operation ammonia could not exercise the slightest influence on the growth and formation of seeds; that in such a

case it is a matter of perfect indifference whether ammonia is conveyed to them or not; for it will not assist in the formation of the constituents of blood, unless the other constituents necessary

sere

moisture, assists also in maintaining the vital processes of plants. But if the subject be treatpered as an unfathomable mystery, the nature of Here their influence will never be known. In medi

dim

cine for many centuries, the mode of action of arid all remedies was supposed to be concealed by used the mystic veil of Isis; but now these secrets have been explained in a very simple manner. An unpoetical hand has pointed out the cause of Crop the wonderful and apparently inexplicable heal1. Ming virtues of the springs of Savoy, by which the inhabitants cured their goitre ;-the waters were lied found to contain small quantities of iodine. In burnt sponges, used for the same purpose, the same element was also detected.

al

"The extraordinary efficacy of Peruvian bark was found to depend on a small quantity of a de crystalline body existing in it, viz. quinine; and dit the causes of the various effects of opium were detected in as many different ingredients of that drug. cause, by ascertaining which we place the actions

1

"Now all such actions depend on a definite

themselves at our command.

"It must be admitted as a principle of agrierts culture, that those substances which have been removed from the soil must be completely restorted to it; but whether this restoration be effected by means of excrements, ashes, or bones, is in a a great measure a matter of indifference. A time will come when plants growing upon a field will be supplied with their appropriate manures prepared in chemical manufactories, when a plant will receive only such substances as actually serve it for food, just as at present a few grains of quinine are given to a patient afflicted with a fever, instead of the ounce of wood which he was formerly compelled to swallow in addition.

"There are some plants which require humus (as a source of carbonic acid) without reproducing it in any appreciable quantity, whilst others can do without it altogether, and actually enrich a soil deficient in it. Hence a rational system of agriculture would employ all the humus at command for the supply of the former, and not expend any of it for the latter; but would, in fact, make use of them for supplying the others with humus.

"We may furnish a plant with carbonic acid, and with all the materials which it may require;

All these conditions are united in the liquid and solid excrements; none of them are absent. In these are present not only ammonia, but also alkalies, phosphates, and sulphates, lphates, in the relative proportion in which they exist in our cultivated

plants."

Our limited space will not allow us to dwell longer upon this portion of the author's work, but we cannot quit it without expressing our conviction that this treatise on the chemistry of agriculture is one of the most valuable works that science has ever presented to mankind, inasmuch as it is eminently calculated to give new powers to industry, in increasing the sources of subsistence, and thereby enlarging the sphere of human happiness.

In the subsequent part of this volume we have, under the general head of the chemical processes of fermentation, decay, and putrefaction:-1. Chemical transformations. 2. The causes which effect fermentation, decay, and putrefaction. 3. Fermentation and putrefaction. 4. The transformation of bodies which do not contain nitrogen as a constituent, and of those in which it is present. 5. Fermentation of sugar. 6. Eremacausis or decay. 7. Eremacausis or decay of bodies destitute of nitrogen: formation of acetic acid. 8. Eremacausis of substances containing nitrogen: nitrification. 9. Vinous fermentation: wine and beer. 10. Fermentation ascribed to the growth of fungi, and of infusoria. 11. Decay

On the mouldering of bodies: paper, brown coal, and mineral coal. Under these heads those mysterious changes of organic matter, called fermentation and putrefaction, the nature of which has hitherto baffled human scrutiny, are clearly and admirably explained. The chapter upon vinous fermentation is a masterly production of the highest order, in which the true chemical nature of that hitherto mysterious phenomenon is explained with admirable perspicuity, and is eminently calculated to confer the most important benefits upon the arts of making wine and beer, both of which, as generally practised, are certainly susceptible of very great improvement by the aid of the new and extraordinary light which has been thrown upon them by the distinguished author. The vinous fermentation, or, in other words, the change of the sugar contained in the must of grapes and in wort into alcohol, depends upon the presence of gluten, which they always contain. When the 'must' of grapes is exposed to the action of the air, as in an open vessel, at the temperature of 60°, or thereabouts, it soon becomes turbid, an intestine action takes place, bubbles arise from all parts of the liquor, a frothy head of yeast forms on the surface, and another portion falls to the bottom of the vessel, the whole or the greater portion of the sugar disappears, and the liquor becomes vinous and intoxicating, that is, the elements of the sugar have undergone a new arrangement, a portion both of its carbon and oxygen have been resolved into carbonic acid gas, which is given off at the surface, while the remainder of those elements of sugar, with all its hydrogen, have assumed the form of alcohol, which remains in the liquor. The immediate cause of this change is owing to the presence of gluten, an azotized substance exceedingly susceptible of becoming oxidized by contact with the air, and of undergoing chemical changes. If the juice of grapes be extracted out of the contact of the air, it may be kept in perfectly close vessels for any length of time without undergoing any change; but no sooner is the air admitted than the vinous change commences, which has been described above. Now this change commences with the gluten, which becomes oxidized by contact with the atmosphere, and the change which it thus undergoes induces a corresponding change in the sugar with which it is in contact, by which its elements enter into new arrangements, that is, they are resolved into carbonic

influence. If there is an excess of sugar, so that the gluten becomes exhausted before the former, the resulting liquor remains sweet, as is the case with the rich wines of the south of Europe. If, on the contrary, the gluten be in excess, as in the instance of the poorer wines of more northern countries, all the sweetness entirely disappears, and some gluten remains in solution. When the latter wines are kept in a cool situation in casks for a great length of time, the excess of gluten becomes slowly oxidized by means of the oxygen which penetrates the pores of the wood, a process which is called ripening, and which renders it but little liable to undergo further change. But if the same kind of wine, instead of being kept in closed casks, and in a cool situation, be exposed to the air, the consequent rapid oxidation of the gluten would induce an oxidation of the alcohol, by which it would be speedily converted into acetic acid or vinegar, and this conversion will be still further accelerated by an increase of temperature.

In the case of malt liquor, though there is an excess of gluten above what is necessary to convert the sugar into alcohol, it does not so readily enter into spontaneous fermentation as wine, and therefore it is assisted by adding to it yeast, which is gluten already in a state of fermentation, and the presence of which soon excites a corresponding action in the gluten of the wort, which in its turn induces the vinous transformation on the elements of the sugar. It is, in fact, a complete case of inoculation. The author observes that

only half filled, without acidifying or experiencby a peculiar management of the wort. perfection of experimental knowledge has here led to the solution of one of the most beautiful problems of the theory of fermentation."

We should be happy to quote the whole of this passage in the author's work, but, even with the fear of obscurity before our eyes, we are compelled to be brief. It has been observed that wort is proportionably richer in gluten than in sugar. In the ordinary mode of fermenting worts the gluten

ec

10

ears

ation

exc

by

1

quantity of malt, and this effect increases in proportion to the degree of temperature of the fermenting wort, producing various and peculiar flavours; and when the fermentation has ceased, a considerable quantity of unchanged gluten remains in solution in the beer, which is the cause, as above explained, of future acidity. These consequences are avoided in the Bavarian process, by a very protracted fermentation at a low temperature, in shallow vessels. In this process the oxidized and precipitating gluten induces the fermentation of sugar, in which itself takes no part. Thus the whole of the saccharine matter becomes converted into alcohol, while, at the same time, the gluten is entirely sepaberated; the removal of which from the beer prevents it from becoming sour in the cask. The decay of woody fibre, the formation ted of humus, mould, the mouldering of bodies paper, brown coal and mineral coal, and poisons, contagions, and miasms, are all cond treated of in the author's usual profound and at the same time perspicuous manner, and ted will be found highly interesting and instructive to persons engaged in those branches of the arts and sciences with which they are

same

close

oft

his c

ol,

E connected.

In the appendix to the first part of this 0% work will be found several very valuable analyses of vegetable substances.

is a

With regard to the author's admirable work Ion Animal Chemistry, which we have read again and again with increasing interest and satisfaction at each perusal, we will only now say respecting it, that few works deserve to rank higher in public estimation, whether we consider the novelty of the writer's views or the sound arguments and profound scientific knowledge by which they Hirare developed.

to

DOS

F.

ART. VII.-1. Report on the West Indian
Colonies. Parl. Paper. 1842.

2. Report on the Western Coast of Africa.
Parl. Paper. 1842. Parts I. and II.
3. The Effect of an Alteration in the Sugar
Duties. By Macgregor Laird, Esq.
4. Fifty Days on Board a Slave Ship. By
the Rev. Pascoe Grenfell Hill.

5. Some Account of the Trade in Slaves.
By James Bandinel, Esq. 1842.

THE first two volumes at the head of our ✓ article contain the evidence collected by two committees of the House of Commons in

the session of 1842: one to inquire into the actual condition, both of negro and of planter, in our West Indian possessions; the other to examine into the state of our settlements on the coast of Africa, the present position and efficiency of our system for the repression of the slave trade, and the prospects of a free emigration from that quarter of the globe. Though, like all their brethren, unnecessarily bulky, they are works of great value, as containing the most trustworthy and authoritative evidence we can obtain on these difficult and controverted topics.

Mr. Laird's pamphlet is most able and most opportune. He has the double advantage of writing with a thorough and personal knowledge of facts, with a clear conception of the great moral and economical principles involved in this complicated question, and with a true and earnest sympathy for the African negro and the English poor. His style is distinct, terse, and vigorous, impossible to misconceive, and not easy to withstand. We are glad to see that the pamphlet has reached a third edition, for it is one which cannot be extensively circulated without producing a strong and beneficial impression.

Mr. Hill's brochure is well deserving the attention of all who feel interested in the welfare of Africa or the suppression of the slave trade. It is a narrative of the occurrence of fifty days passed on board a slaver between the period of her capture by one of our cruisers in the Mozambique Channel, and the landing of her slaves at the Cape. It draws a simple but a fearful picture of the cruelty of our system of armed repression, and of the terrible aggravation of the sufferings of the wretched victims of our humanity consequent thereon; and the unpretending and unexaggerated tone in which it is written must carry conviction home to every mind. Those who, after the disclosures contained in the works of Mr. Laird, Mr. Hill, and Sir T. Fowell Buxton, still uphold the system at present followed by our cruisers and maintained by our government, must be alike impassible to argument and evidence.

With the help of the above works we propose to lay before our readers a succinct view of the relation between the two great subjects which at present occupy so much of the public attention, -the slave trade and the sugar duties.

In order to prevent misconception at the outset, and to save the necessity of future precautionary protestations, it may be well to state that we are, and always have been, earnest enemies of slavery; that we advocate the principles of commercial freedom in their widest signification and their most unreserved extent; that we are sincere friends to the West India planters and to the cause of African civilisation.

The present position of this great series of national questions may be stated thus. About thirty-five years ago England prohibited the slave trade to her own subjects, and since that time has been unceasing (and unquestionably most sincere and zealous) in her efforts to prevent others from engaging in it, by treaties with foreign powers, and an armed squadron on the coast of Africa. In these efforts worthy of all praise as far as their object is concerned; worthy of all condemnation as regards the wisdom of the means she is calculated to have spent considerably upwards of fifteen millions sterling.* Yet not only has she entirely failed in her object, the slave trade having increased in extent in spite of her exertions, and been infinitely augmented in the degree of suffering it inflicts in consequence of those exertions; but in the course of her efforts she has not unfrequently found herself obliged to violate the most acknowledged principles of international law, and has thereby in

* "Great Britain has expended in bounties alone upwards of 940,000l., and in the maintenance of the courts established for the adjudication of the captured slaves, above 330,000l.; besides a large sum annually in supporting a considerable force of cruisers in various parts of the world, to intercept and destroy the traffic. This expenditure, together with that caused by the payments to foreign powers on account of the slave trade, for the support of liberated Africans, and for other incidental expenses, may be shown, from official documents, to have amounted to upwards of fifteen millions sterling." - Prospectus of the Society for the Civilisation of Africa, prefixed to Sir T. F. Buxton's book, p. 2.

† See for instances, Bandinel, p. 175, also, pp. 224, 225. We also wish to draw particular attention to the following official document :

And

curred the hatred of every maritime power in Europe and America, and on more than one recent occasion narrowly escaped involving herself in actual hostilities.* it has now become a question among sincere abolitionists whether, both for England herself, and for the miserable objects of her mis-called protection, it would not be desirable, and may not be necessary, to withdraw our squadron, and abandon-if not our object - at least that mode of prosecuting it.†

After the legal abolition of the slave trade, the English people began to reflect, justly enough, that their work was incomplete, unless they could eradicate slavery itself, first in their own dominions, and then by example, or diplomacy, or force, throughout the world. A society was formed, having this most desirable object in view, and was supported by a numerous and able party in the legislature. The project was zealously advocated on one side of the Atlantic, vehemently reprobated and resisted on the other; but no efficient steps were taken by either party to effect those preparatory measures which, in the eyes of all, were essential to the beneficial operation of the proposed change. The West India planters felt like men who were about to be robbed by a stronger party, and took refuge in a dogged

in slavery, unless the power upon whose territory or within whose jurisdiction the factories or the slaves are found should, by treaty with Great Britain, or by formal written agreement with British officers, have empowered her Majesty's naval forces to take these steps for the suppression of the slave trade; and that if, in proceeding to destroy any factory, it should be found to contain merchandise or other property which there may be reason to suppose to belong to foreign traders, care should be taken not to include such property in the destruction of the factory.

"With respect to the blockading rivers it appears, from the papers referred to, that the terms 'blockake' and 'blockading' have been used by British naval officers when adverting to the laudable practice of stationing cruisers off the slave-trading stations, with a view the better to intercept vessels carrying on the slave trade, contrary to treaties between Great Britain and the powers to which such vessels belong.

"But as the 'blockade,' properly used, extends to an interdiction of all trade, and indeed all communication with the place blockaded, I beg leave to submit for your lordships' consideration, whether it will not be proper to caution her Majesty's naval officers upon this head, lest by the inadvertent and repeated use of the term 'blockade,' the exercise of the duty confided to British officers in suppressing slave trade might by any one be confounded with the very different one of actual blockade.

I have, &c.

(Signed) "ABERDEEN."

* The existing state of our relations, both with France and the United States, afford an exemplification.

† "If we succeed in establishing a blockade of the coast, together with a confederacy on shore, and proceed no further,

it will still be doubtful, as it has been in our former operations (?), whether more of good or of evil will be effected; -good, by the degree of restraint imposed upon the traffic, or evil, by

rendering what remains concealed and contraband; and when I recur to the fearful aggravation of the sufferings of the slaves, which has already arisen from this cause, I am almost disposed to think that it were better to do nothing than to do only this."-Buxton, p. 300.

All the first authorities among the abolitionists are agreed upon this point, as may be seen by a reference to the quotations from their statements in Appendix A of Mr. Laird's pamphlet, particularly at p. 71.