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found, on comparing his barometric measures with certain heights, trigonometrically determined by M. Ramond in the Pyrenees, to require a small correction. The coefficient, thus adjusted, was found by Biot to agree perfectly with the experiments on the specific gravity of mercury when accurately repeated; and his experiments also gave the same refraction which Delambre had deduced from astronomical observations.
In the prosecution of these experiments, M. Biot found that the refracting power of different gases affords means more accurate than the ordinary processes of chemistry for inquiring into the composition of certain substances, such as the diamond, which he concluded to be partly composed of oxygen. The idea of inferring the chemical composition of bodies from their refracting power, as is well known, was first conceived by Newton: it seems to have been much extended and improved on by the philosopher just named.
It is not taken notice of in the Report, but we think it right to remark it, that the rule for barometric measurements had been investigated on strict mathematical and mechanical principles long before it was done by Laplace, and formulas brought out, which do not materially differ in their results, though they do considerably in their forms, from that of the French geometer. After Deluc made his improvements, and discovered by trial the very
simple rule which he employs, leaving it however quite empirical, and not deduced from principles, a geometric demonstration of that rule was given by Dr Horsley in the Philosophical Transactions. An investigation of the same, purely analytical, was published by Professor Damen of Leyden; and a third, which considers the problem with great generality, and takes into view several circumstances which had not hitherto been attended to, is given by Professor Playfair in the first volume of the Edinburgh Transactions. The investigation of Laplace, therefore, was not entirely new as to its object or its principles, though we believe his method to be original, and in all respects worthy of its author. His rule, even when corrected as above mentioned, does not perfectly agree with that which we employ in this country, of which the form is agreeable to the investigations just mentioned, and the coefficients determined from the excellent experiments of General Roy and Sir G. Shuckborough. It is also less commodious in practice than either our formula or that of M. Trembley of Geneva. We are not, however, perfectly prepared to state in what the difference consists, or to what extent it goes. As the question now stands, we think a comparison of the different barometric formulas is an excellent subject for a mathematical memoir.
Under the article of Magnetism, the Report mentions the series of observations published by
M. Gilpin in the Philosophical Transactions for 1806, from which some curious results may be deduced concerning the secular variations of the magnetical meridian. Another article relates to Dr Wollaston's apparatus for. measuring, in a manner extremely simple and accurate, the refraction of transparent bodies, (Phil. Trans. 1802.) It is said, that a very valuable addition to this apparatus has been made in France, by M. Malus; and that an analytical consideration of the subject had enabled him to correct an error which had escaped Dr Wollaston. We do not know if We do not know if any more particular account of M. Malus's improvement has yet reached England.
The next object of Delambre's Report, is Geography and Travels. On this he is very short, and only runs over some of the principal occurrences. "The taste," he says, " to which the successful and brilliant voyages of Bougainville and Cook had given rise, was not weakened by the disastrous, though not useless, expeditions of Peyrouse and Entrecasteaux. Deputies from the African Society in England, penetrated into countries entirely unknown. Horneman met with the most distinguished reception from the conqueror of Egypt; Mungo Park braved the greatest dangers; and Flinders exposed himself to the most dreadful risks, in order to explore Van Dieman's Land, and the coast of New Holland. The ambassadors of the
English penetrated into Thibet, into the kingdom of Ava, and into China. Vancouver described the coast he was appointed to survey, with a care and exactness proper to serve as a model for all those who have similar duties to discharge."
We cannot help remarking, on reading the name of Flinders, that the fate of that skilful and intrepid navigator, at this moment, we believe, languishing in confinement in the Isle of Bourbon, does great discredit to the government of France. Accident put him in the power of France. A voyager, engaged in the cause of science, had a right every where to look for friends. Flinders was treated as an enemy. His release, however, was at length agreed to; and orders to that effect sent out to the governor of the Isle of Bourbon: but hitherto, if we are rightly informed, these orders have not been complied with.
The Report goes on to mention what the French did in Egypt; the voyages of Marchand, Baudin,
Lastly," (says Delambre,)" to terminate this sketch with an expedition which contains in it every kind of merit, Humboldt has executed, at his own expence, an enterprise that would have done honour to a nation. Accompanied only by his friend Bonpland, he has plunged into the American wilderness; he has brought back with him 6000 plants, with their descriptions; has determined the position of 200 points, by astronomical observation;
has ascended to the top, and has measured the height of Chimboraço. He has created the geography of plants, assigned the limits of vegetation, and of eternal snow; observed the phenomena of the magnetic needle and of electric fish, and has presented the lovers of antiquity with much valuable information concerning the Mexicans, their language, their history, and monuments."
A sketch of these curious travels is given in one of the notes, at the end of the Report, but would lead us into too long a digression.
Delambre then concludes his Report with a new address to the Emperor. The Institute had it in command, it seems, not only to report on the actual state of the sciences, but to suggest the measures that would promote their further advancement. In this part of his task, Delambre has acquitted himself well, and with considerable address.
"Votre Majesté daigne interroger l'Institut sur les moyens d'assurer les progrès ultérieurs; les progrès des mathématiques ne sont nullement douteux, l'instruction première trouve des sources abondantes dans tous les lycées; l'ecole polytechnique est une pépinière de sujets distingués pour tous les genres de service public.-La loi bienfaisante qui a régeneré l'instruction, promettait une école spéciale aux mathématiques; cette école existait. La Géométrie et l'Algébre, l'Astronomie et la Physique sont professées au Collége Impérial de France.