(J. C. E. Le Michaud D'), a French engineer and military writer of eminence, and memorable as the inventor of the Floating Batteries employed against Gibraltar, was born at Pontarlier in the year 1738. He was originally destined for the church; but, instead of employing himself in the studies suited to that profession, he became wholly engrossed with plans of fortifications, and was at length admitted, with the consent of his parents, into the Corps of Engineers. He distinguished himself at several sieges during the seven years' war; and had acquired so much reputation by his professional services and by his writings, that he was specially employed to assist in the last grand effort made by France and Spain for the reduction of Gibraltar, in 1782. It was about this period that he projected the famous floating batteries; an invention which inspired the combined armies with the greatest hopes of success, and which at first occasioned no small degree of alarm in the British garrison. "The battering ships," says Drinkwater, in his interesting account of this memorable siege, "were found to be no less formidable than they had been represented. Our heaviest shells often rebounded from their tops, whilst the 32 pound shot seemed incapable of making any visible impression upon their hulls. Frequently we flattered ourselves they were on fire; but no sooner did the smoke appear, than, with the most persevering intrepidity, men were observed applying water, from their engines within, to those places whence the smoke issued." Of the ultimate fate of these expensive and formidable engines of attack, all British readers must be sufficiently informed. Not one of the whole ten escaped destruction from the bombs and red-hot balls poured upon them from the garrison. M. D'Arcon, however, published a memoir to show, that his batteries were wilfully exposed to destruction through the envy and jealousy which the contrivance had excited among the Spaniards; and this statement seems to have obtained the general concurrence of his countrymen. But projectors do not readily admit any inadequacy in their schemes; nor will a vain-glorious people, who have been foiled in war, ever ascribe their disgrace to the superior skill or constancy of their enemy.
M. D'Arcon appears in the capacity of a General in the first years of the Revolution; and, in particular, was employed in the invasion of Holland, where, in 1793, he besieged and took several fortified places. He soon afterwards withdrew, or was driven from public life; and remained in retirement till 1799, when he was made a member of the Conservative Senate by Bonaparte. He died the following year, aged sixty-seven. He was a member of the Institute, and author of the following works:—1. Réflexions d'un Ingenieur, en réponse à un Tacticien, 1773, in 12mo. 2. Correspondance sur l'Art de la Guerre, entre un Colonel de Dragons et un Capitaine d'Infanterie, 1774, in 8vo. 3. Défense d'un Système de Guerre Naturelle, &c. 1779, in 8vo. 4. Mémoires pour servir à l'Histoire du Siège de Gibraltar, 1783, in 8vo. 5. Considérations sur l'Influence du Génie de Vauban dans la Balance des Forces de l'Etat, 1786, in 8vo. 6. Examen détaillé de l'Importante Question de l'Utilité des Argyreshire.
Places Fortes, et Retranchements, 1789, in 8vo.
De la Force Militaire Considerée dans ces Rapports
Conservateurs, 1790, in 8vo.
Considerations Militaires et Politiques sur les Fortifications, 1795, in 8vo.
This work was published at the expense of the Government, and contains a sort of digest of all his observations and opinions on military subjects.
See Biographie Moderne, Tom. I., and Biographie Universelle, Tom. II.
Arcy (Patrick D'), Member of the Academy of Sciences of Paris, a general officer in the French army, Chevalier of the order of St Louis, &c. was born in Ireland in 1725. His parents, in consequence of their attachment to the House of Stuart, left Ireland, and settled in France. He studied Mathematics with distinguished success under Clairaut the elder, and had for his fellow-student the celebrated Clairaut the son. He obtained a commission in the French army; and, in 1746, was embarked in the expedition which was intended to make a descent in Scotland. He was made prisoner, and was treated like other prisoners of war, no notice being taken of his having been born a British subject. He continued attached to the House of Stuart during the whole of his life.
In 1760, he published his Essay on Artillery. To estimate the force of the explosion of gun-powder, he employed a cannon suspended, so that the arc of vibration described by it on its being fired, was a measure of the force of explosion. To measure the initial velocity of a projectile, he used Robins' machine. Robins showed, that when the velocity of a projectile is great, the resistance opposed by the air is not in proportion to the square of the velocity, as is the case when the velocity is small. D'Arcymade experiments with a view of ascertaining this law, but without success. His work contains an account of experiments made by him to determine the most advantageous length of cannon. He published a paper on hydraulic machines in 1754, where he treats of the maximum of effect of water-wheels. He also published a paper concerning the duration of the impression of light on the retina. He found that the revolution of a luminous point must be rapid, so as to be performed in \( \frac{1}{6} \) of a second at the least, in order to produce the appearance of a continued luminous circle.
He was of a handsome figure, and passed much of his time in the gay world. A short time before his death he married a young lady his niece, and took the title of Count. Although attached to the House of Stuart, and therefore inimical to the English Government, yet he admired the national character of the English, and was attentive to English travellers. He died in 1779, and was succeeded at the Academy by the Abbé Bossut.