exhaust them, though scarcely sufficient to raise a leaf from the ground. The account given by Mr. Ives is, that it blows over the desert (of Syria) in the months of July and August, from the northwest quarter, and sometimes continues with all its violence to the very gates of Bagdad but never affects any body within its walls. Some years it does not blow at all and in others it comes six, eight, or ten times, but seldom continues more than a few minutes at a time. It often passes with the apparent quickness of lightning. The sign of its approach is a thick haze, which appears like a cloud of dust rising out of the horizon, on which they throw themselves with their faces on the ground, as already mentioned. Camels are said, instinctively, to bury their noses in the sand. As for the stories of its dissolving the cohesion of the body in such a manner that a leg or an arm may be pulled away from those who are killed by it, or that their bodies are reduced to a gelatinous substance, we cannot by any means give credit to them. From its extreme quickness, and luminous appearance, it would seem to be an electrical phenomenon immediately preceding those vehement hot winds which all travellers agree in likening to the vapour issuing from a large oven when the bread is newly taken out. Its electrical nature will be more probable from the account given by Mr. Ives, that the Arabians say it always leaves behind it a very sulphureous smell. These particulars do not at all accord with the supposition of its consisting of fixed air. I have indeed been assured by a gentleman long in the service of the English East India Company, that the samiel cannot pass over a river. Hence probably it has been supposed to be a blast of fixed air, because this species of gas is readily absorbed by water; but we know that the same thing would also take place with any quantity of electric matter; for water takes up this also much more completely than it does fixed air. The _mofetes_ are invisible, and kill in an instant. They rise from old volcanic lavas, and, as it were, creep on the ground, and enter into houses, so that they are very dangerous; but, though they may probably consist of fixed air, we have not as yet any direct proof of it. It is not indeed easy to imagine why any lava should suddenly emit a great quantity of fixed air, and then as suddenly cease; nor in what manner the air thus emitted should continue unmixed with the atmosphere; for fixed air will very readily mix in this manner, insomuch that a large quantity of it being let loose in a room has been found to vanish entirely in less than half an hour. Sir William Hamilton mentions a mofete having got into the palace of the king of Naples.