taken by the former, and by the present governor. The soldiers were every morning lightly moistened with oil, which proceeded in constant exhalation from the heat of their bodies, and thereby prevented the possibility of the contagion affecting them. Tobacco was profusely smoked, and burnt in the dwellings of the inhabitants, who, during the prolonged quarantine, felt very uneasy to resume business. They beguiled their evenings by walking on the terraces, the tops of the houses being all, or principally, flat. There friends and lovers used to enjoy the pleasure of beholding each other at a distance, while Retracing long those walks with weary feet, They cursed the fate which warned them not to meet! When the quarantine ceased, they hastened eagerly to learn the fate of their friends, in the same manner as sailors hurry below after battle, to see how many of their messmates have survived to share in the dream of glory! Before leaving Malta, I had the melancholy satisfaction of standing on the ruins of the plague-hospital, which had been burnt to ashes-that place where so many hopes and fears were hushed to rest! It gave rise to dismal recollections! May none of my readers ever behold the miseries of the plague, or endure the lingering tantilization of the quarantine! THE ART. VIII.-New Steam Engine. HE following steam engine, constructed under the direction of colonel Ogden of New Jersey, and intended for a steam-boat to ply to and from Norfolk in Virginia, seems calculated to give equal power, with diminished fuel, and dispensing with some of the apparatus commonly in use. The prodigious importance of steam engines seems now well understood, and any attempt to improve them deserves attention on part of the public. C. The principal object in the construction of this engine is, a saving of the expansive power of the steam; which in ordinary ones is either entirely disregarded, or by being effected in a single cylinder, of necessity increases its size to an inconvenient degree, (an objection noticed by Mr. Watt in his elucidation of the subject-vide Encyclopedia, Art. Steam, &c.) besides adding to the already irregular motion it is subject to, and which even a balance-wheel cannot entirely obviate. Steam is subject to the same law as other expansive fluids,-compressed to half its volume, it acts with double force, or expanded to twice, with precisely half: thus, if of the original power of ten pounds to the inch, it be admitted into a cylinder during half the stroke, and then shut off, it will continue to exert a decreasing power, until at the close it will be at five, its expansion will consequently be the mean (about seven.) If therefore the steam be used in two cylinders, each alternately half filled, the expansive power operating in one, while the full power is exerted in the other, both acting simultaneously on the same shaft, it is clear, that without loss of time or inequality of motion, the whole of that expansion, or seventy per cent. will be added to the power of the engine. If the same quantity of steam be used in a single cylinder of double area, and to obtain the benefit of expansion, shut off at half stroke, there will be at every closing of the valves, a revulsion in the boiler that must certainly be more destructive to its duration than if the expenditure were in an uninterrupted stream. 'The secondary advantages arising out of this construction are, The gearing being to cranks at right angles with each other, when the one is at its minimum or dead point, the other being at its maximum, will carry it past the centre, and (the one gaining at the same rate that the other is losing power) will perfectly equalize the motion, and thereby do away the necessity of a balance or fly-wheel. The engine may be started off from any point it may happen to rest at, without the trouble that frequently occurs in the single ones of prying past the centre. As either cylinder may be worked separately, by throwing the other out of gear, the chances of accident are not so great, nor the effect so much to be apprehended, for should a derangement occur to any part of the machinery of one engine, its corresponding part in the other will be capable of performing the duties in both.' The most important advantage to be derived from this construction of the steam engine, is the addition of the expansive to the original power of the steam from the boiler, of whatever elasticity. Steam when enclosed, having a space in which to expand to twice its original volume, acts with a power which is in a ratio, according to the demonstration of Mr. Watt, (vide Encyclopedia, Art. Steam, plate 478, fig. 10-1st American edition,) to its original power, as 170 to 100. Thus, if the power of steam admitted from the boiler uninterruptedly into the cylinder, during the whole stroke, be as 100, it will act, if shut off when the cylinder is half filled, (that is with 50) with a power equal to 85. If, therefore, there are two cylinders, by means of which the steam be made to act on the same machinery, and if the steam be admitted into each during half the stroke only, and suffered to act by its expansive force during the other half, but in such manner that when shut off from one cylinder it is immediately admitted into the other, then there will be always acting on the machinery a power of steam equal to that of the full stream from the boiler, in addition to the power which steam possesses of expansion. Therefore, one cylinder full of steam is, by this means, made to act with the original power of unexpanded steam, and also with that of steam expanding to double its volume. Thus, with a boiler capable of supplying one cylinder full of steam at every stroke of the piston, as is the case in the ordinary engines of Boulton and Watt, rating the power at 100, a power is obtained from the same steam, with two eylinders, equal to 170. A 100 100 100 50 B Suppose the power applied in either cylinder, be equal to raising the weight 100 Suppose it lifted by B to its present situation, and the communication from the boiler to B then closed, and opened to A-it follows, that as the power in A will, of itself, be sufficient to raise the weight, the expansion, whatever it is, in B, will be added to the 100 in A-And as all elastic fluids, occupying double space, act with half pressure, the power in B, when the piston shall have arrived at the top of its stroke, will be equal to 50; the gain will, consequently, be the mean between that and 100. A second, and certainly not unimportant advantage is, that as the communication of the power from the two cylinders to the cranks is at right angles, and both act on the same leading shaft, it will always be equalized; as, when one crank is at its dead point, the other will be at its strongest; and they will thus mutually assist each other, thereby doing away the necessity of balance-wheels, always inconvenient on board of vessels. In consequence of this a more convenient arrangement can be made with the machinery, by which it may be more safely protected in vessels of war, &c. This engine will be much less liable to derangement, as, from its construction, should an accident happen to any part, there is always a corresponding one capable of performing the functions of both. When the wind is strongly adverse, an engine is unable to make its usual number of revolutions; from eighteen or twenty strokes per minute it is sometimes reduced to ten or twelve, and, consequently, the surplus steam must be suffered to escape from the safety valve: with two cylinders this will be entirely obviated, as whatever may be the quantity of steam generated, it can all be used by altering the time of shutting off in the cylinders, and thus the power will be increased with increased resistance. ART. IX.-Notoria; or Miscellaneous Articles of Philosophy, Literature, &c. Account of Mr. Burckhardt, the celebrated traveller in Africa.-From the Quarterly Review of June 1818. Mr. J. L. Burckhardt, a cadet of one of the principal families in Switzerland, was a native of Zurich. At the time when the despotism of France had closed every avenue, but one, of distinction to the youth of the continent, our young traveller, unwilling to engage in the career of a military life, came over to England, with an introduction to sir Joseph Banks, and after a few months' residence in London, offered his ser vices to the African Association. The result of Park's first attempt had more effect in kindling his hopes of final suc cess, than the fate of Houghton, Horneman, and Ledyard in depressing them. Possessed of a good constitution, and unimpeached moral character, well educated, and capable of improving his talents by application in whatever pursuit might be found necessary to qualify him for the undertaking, he was immediately enlisted into the service of the association, and received from various quarters every assistance he required in the different branches of science, to which his attention was directed. Mr. Burckhardt left England on the 2d of March, 1809, for Malta, whence he set out for Aleppo, which he reached on the 6th of July following. Here, and at Damascus, he spent a principal part of the next three years; during which he made a variety of excursions into the Hauran and the Lesge, visited the ruins of Palmyra and Baalbec, passed some time among the Turkmans of the northern provinces of Syria, and perfected himself in the knowledge of the religion, manners, and language of the Mahommedan Arabs, by frequent and long residences among the Dedouins of the desert. The result of his researches in that part of the world, which he considered as merely preparatory to his great enterprise, the African Association now possess, in the form of journals, and of political, geographical, and statistical notices. On the 18th of June, 1812, he set out from Damascus for Cairo, avoiding the usual route of the sea coast and desert between El Arish and the borders of Egypt, and directing his course, in the disguise of the poorest of the Bedouins, from the Holy Land, east of the Jordan, by Szalt, into Arabia Petræa, and across the great desert El Ty: he reached Cairo on the 4th of September, with the intention of availing himself of the first opportunity of penetrating into Africa, which the departure of a Fezzan or a Darfour caravan might afford him. Finding, however, that this was not likely soon to take place, he determined to pass the intermediate time in exploring Egypt and the country above the Cataracts, and was thus enabled to perform two very arduous and interesting journies into the ancient Ethiopia; one of them along the banks of the Nile, from Assouan to Dar El Mahass on the frontiers of Dongola, in the months of February and March 1813, during which he discovered many remains of ancient Egyptian and Nubian architecture, with Greek inscriptions, such as are found in the temples of Phila; the other, between March and July, in the following year, through Nubia to Souakim and Djedda. The details of this journey contain the best notices ever received in Europe of the actual state of society, trade, manufac tures and government, in what was once the cradle of all the knowledge of the Egyptians. Our traveller's next excursion appears to have been from Cairo into the peninsula of Arabia, for the purpose of visiting the holy cities of Mecca and Medina; in the former of which he resided between four and five months, making his observations secure under the character of a Mahommedan Hadje or pilgrim, and with all the advantages of the perfect knowledge which he had now acquired in the religion, language and manners of the inhabitants. His residence in this part of the east necessarily brought him into contact with the Wahabees; and the Association have received from him, besides a full description of Mecca, and of the early and recent superstitions of that part of the world, a very elaborate account of the rise and progress of this extraordinary set of Mahommedan puritans, comprehending the whole of their political history from the foundation of the sect, between fifty and sixty years ago, by Abd El Wahab and Mohammed Ibn Saoud, to the peace between Abdullah Ibn Saoud and Tooson Pasha, on the part of Mohammed Ali, pashaw of Egypt, in 1815. The last excursion of Mr. Burckhardt was from Cairo to Mount Sinai, and the eastern head of the Red Sea. The journal of this interesting tour is interspersed with a variety of historical notices on the former state of the country, and annexed to it is a memoir of the wanderings of the Israelites on their departure from the land of Pharaoh. Besides these works, we are happy to learn that the Association are also in possession of a variety of notices on the interior of Africa, with several vocabularies of African languages, collected from the natives who visited Egypt during Mr. Burckhardt's detention in that country. There is also a series of nine hundred and ninety-nine Arabic proverbs, in the original language, together with English translations and illustrations of the various allusions contained in them; to these is added a literal and spirited translation of a burlesque epic poem, in the vulgar dialect of Cairo; the subject of which is a contest between wine and bast, the latter being a generic term for all the intoxicating substances com |