visionary schemes, which have been so often tried, and have so often failed; and a renewal of which, under any circumstances, would prove abortive, and could only cement more strongly the power of France, and again deluge the continent with blood.

Mr. Whitbread thinks that we should first attempt by ne gociation the end which we propose by the prosecution of hostilities; the emancipation of Spain, and eventually of Europe from the power of France. If, indeed, we were to attempt to treat with France before we sent succours to the Spaniards, the conditions which Mr. W. suggests, would be such as are most consistent with the honour and the probity of the country; but considering the perfidy and the temper of the emperor of the French, we think that any present attemat to negociate would be injurious to the interesis both of Britain and of Spain. When the Spanish patriots have driven the French troops beyond the Pyrenees, and Bonaparte is alarmed by the menacing aspect of the east and of the north, most favourable juncture will arrive for negociating a peace, which may humble the pride of France, and preserve the independence of Europe.

ART. XVI.—An Inquiry into the Changes induced on Atmos pheric Air by the Germination of Seeds, the Vegetation of Plants, and the Respiration of Animals. By Daniel Ellis. 8vo. Murray, 1807.

THE quantity of original experiment contained in this Inquiry is not considerable; but the collection of facts is extensive; and proves the author to have been industrious in his researches, whilst his reasonings bespeak no common share of talents for philosophical investigations. The result of these inquiries lead to the establishment of the uniformity of the operations of nature in the processes which seem of the most immediate necessity in the conservation of the vital principle in all organised and living beings. The rudest observations must have taught mankind the necessity of the perpetual application of air to the animal organs for the support of life. More attentive and curious remark has shown that the vegetable world is equally indebted to the atmosphere for the qualities which distinguish it from lifeless and unorganised matter. Though vegetables preserve their external form and physical properties longer under the deprivation of atmospheric air than the greater number of ani

mals, still they inevitably perish, if the deprivation be continued long enough. Nor is there a single moment of its existence (if we exclude the very first period at which the seed begins to germinate,) in which the presence of atmospheric air is not equally and essentially necessary.

The more accurately these phenomena have been observed the more uniform do they appear in all the orders of living beings; wherefore, a connected view of these processes in the different orders, beginning with those whose structure is most simple,(or what appears so to us) and rising to the most complicated cannot but be interesting to the physiological inquirer. To present this view is the object of Mr. Ellis's work; and at the same time he has laboured much to improve the theory, which is still imperfect, owing probably to the want of sufficient data, notwithstanding so many inquirers have engaged in this field of investigation.

The first chapter of this Inquiry treats of the Germination of Seeds; and it would seem from the simplicity of experi ments requisite to elucidate the subject, that it would be no difficult matter to arrive at precise and accurate results Still there are points which are by no means perfectly ascertained. What is certain may be comprised in a few words, for the beginning of germination water and a proper temperature are only necessary. For its continuance the presence of oxygen is essential, and accordingly the oxygenous portion of the atmosphere is at length entirely destroyed by the process of germination; in its place carbonic acid is found, and the nitrogenous portion of the air seems quite unaffected. Such are nearly all the facts which have been thoroughly established, whilst there are many others, on which the opinions of philosophers have been greatly divided. Is the oxygen absorbed by the seed? Is the whole of it employed in the formation of carbonic acid? By what process (if the carbonic acid is formed exterior to the seed,) is carbon acidified in so low a temperature? Mr. Ellis both on the subject of the germination of seeds, and also in the vegetation of plants,and respiration, adopts the hypothesis that there is no absorption of oxygen either by the seed, by the plant, or by the animal; but that universally carbon is emitted as a species of excretion, and that the oxygen combines with it exterior to seed, plant, or animal. If this be true, the whole of the oxygen is of course expended in the formation of carbonic acid.

He observes that

oxygen gas to be taken up by the seed by the

t

operation of chemical affinity, necessarily implies its previous separation from the nitrogen gas with which it was united; but how could this be done unless the seed presented something to the air, which had a stronger affinity to its oxygen than the nitrogenous portion has? And what could it offer but moisture and carbon? Moisture however does not decompose air; and if carbon be the agent must not carbonic acid be at once formed? And if this acid be thus formed, exterior to the seed, and out of the oxygen gas in contact with it, how can we hold that gas to be first singly taken in by the seed, and expelled afterwards in the form of carbonic acid? To say that the air is attracted in its undecomposed state, necessarily requires proof of the existence of certain cavities in the seed where it can be retained for as the nitrogen gas neither suffers nor pro duces change, it must be completely expelled after the oxygen is abstracted from it. Lastly M. de Saussure has endeavoured to show that the carbonic acid formed in germination contains in it precisely the quantity of oxygen gas that has disappeared and although, from the difference of opinion which prevails concerning the actual proportions of the elements which constitute this substance this cannot be positively assumed, yet the near proportions which, in our own experiments, as well as in those of Saussure and Cruickshank, the two gases bear to each other at the beginning and end of the process, renders it extremely probable. If this opinion be well founded, no part of the oxygen can be retained by the seed, and we may conclude, therefore, with M. de Saussure, that none of it is either attracted or absorbed.'

It is obvious that much of this reasoning is founded more upon the argumentum ad ignorantiam than any direct proof of the system Mr. E. wishes to establish: this too is the sort of argument which may be retorted by an adversary with equal force. It may in return be very properly asked, how can carbon unite with oxygen in the common temperature of the atmosphere? Experiment seems to be in direct contradiction to the possibility of such an union. If nothing is necessary but the excretion of carbon; if the oxygen is neither absorbed, nor even in its proper form comes in contact with the secreting membrane, what is the office that it performs? To convert, it will be said, the carbon into an acid. But this being done out of the body, why should death immediately ensue from its suspension, though but for two or three minutes? If therefore this hypothesis is really correct, and it shall be proved that the carbonic acid is really formed exterior to the organized substance, from which it seems to be emitted, we think it most probably the effect of some double decomposition, the elements of which have not hitherto been thoroughly ascertained. Besides, it is allowed that carbonic acid is emitted from the seed when there is not

a particle of oxygen present, but when the seed is confined entirely in nitrogen or in hydrogen gas. We think it not a sufficient answer to say, that in this case germination is wholly at a stand, and the carbonic acid arises from a decomposition of the substance of the seed. We know that a similar and partial decomposition is not perpetually going on during the progress of germination; and doubt not that in all animal bodies, likewise, a part of their substance is undergoing an analogous decomposition, which it may be improper to term putréfaction, but which probably in many points resembles the first stage of it. We have noticed this point more particularly now, that we may be spared the necessity of recurring to it in our review of the remaining parts of the work, since Mr. Ellis has transferred the same chain of argument which he uses on the subject of germination to vegetation and respiration. We must confess that he has supported his hypothesis with considerable ingenuity; but we are not satisfied that he has determined the question, and wish that he had been more anxious to increase our stock of facts than to accommodate those we already possess to a preconceived and doubtful hypothesis.

The second chapter of the work treats of the changes in duced on the air by the vegetation of plants. After distinctly recounting the agency of moisture, heat, and light, he is na turally led to advert to a theory of Dr. Priestly, which has been very generally adopted, though even at its first proposal the evidence in favour of it was very defective. But the supposed beauty of the final cause which it seemed to disclose, has induced both chemists and physiologists to examine very superficially the facts upon which this opinion has been maintained. The theory we allude to is that which attributes a melioration of the atmosphere to the growth of vegetables; so that it was concluded that the process of vegetation was in its consequences directly the reverse of respiration and combustion. This opinion, it must be remembered, in behalf of a man of deserved eminence, and who we believe, though often mistaken, never wilfully supported a falsehood on any subject whatever, was adopted before its author had discovered any correct means of analyzing the air; and subsequent facts, though they did not seem strong enough to require him formally to retract his opinion, yet obviously shook his confidence in his former conclusions, and his mind seems finally to have remained in a state of uncertainty on the point. The experiments of the accurate and sagacious Scheele were uniformly in contradiction to Dr. Priestly's inferences; and finally, Mr.

Ellis has in this chapter of his work, so fully disproved them, that we doubt not that the question may be considered as finally put to rest. Dr. Ingenhouz and Mr. Gough bave shewn that vegetables, like animals, do not grow in pure nitrogen gas;, but if either atmospheric air or oxygen gas have access to the leaves, they vegetate freely; oxygen gas is therefore necessary to vegetation. Dr. Woodhouse shewed that carbonic acid is produced in the process of vegetation. Mr. Ellis has confirmed those experiments; he has found the oxygen of the air to disappear, carbonic acid to be formed; and by contriving to make the vegetables grow without the aid of mould (as mustard seed will upon moistened flannel) he has proved that the acid is formed by the vegetable itself in contact with oxygen gas. If the plants be kept confined in a portion of common air long enough, every particle of oxygen disappears, after which the plants decay, and when withdrawn yield a putrid smell. In vegetation, as in germination, the nitrogen gas of the air seems to be wholly inert,

Another idea, which seems equally unfounded, is that carbonic acid is taken up by the vegetable, which has been supposed to retain its carbon, and to emit its oxygen. The experiments of Mr. Ellis completely refute this notion, which involves the strange incongruity of supposing the same substance to be at once both a species of food and excrement. Saussure, indeed, has been said to have destroyed the vegetation of plants by inclosing a quantity of lime in the vessels in which they were eonfined. But granting the correctness of the experiment, it by no means follows that the effect is produced by the absence of carbonic acid. Lime absorbs water with much greediness: and Mr. Ellis supposes with much probability that to the abstraction of moisture is owing the destructive effect upon the plant, and he has confirmed this explication by some direct experiments properly adapted to that end. It must undoubtedly be alJowed that a solution of carbonic acid in water is decomposed by solar light acting on the leaves of vegetables; but the experiments of Count Rumford bave proved that the orga nized structure of the leaf is not essential to the separation of oxygen in this experiment: dried leaves, fibres of raw silk, and even glass serves as well. But were it even otherwise, Mr. Ellis well observes, that the circumstances are so different from those of natural vegetation, that they cannot be received as proofs of the same actions.

The changes produced in air by animal respiration are treated of in two chapters; one appropriated to the respi