[63] Gas is a German word, or derived from one, signifying spirit. The word ghost comes from the same original.
[64] This must be understood only of its general properties and effects; for, though the fume of charcoal possesses many of the apparent properties of pure fixed air, it contains also a very considerable quantity of another kind of gas.
[65] Many fabulous stories have been related concerning the samiel. Even so late a traveller as Mr. Ives has adopted some of those exaggerated accounts which have been discredited by those who have long resided in the countries where this wind is commonly met with. It is not peculiar to the deserts of Arabia, but is met with in all hot countries which are destitute of water. In the African deserts therefore it is common; and Mr. Bruce describes it by the name of simoom. It was preceded by whirlwinds of a very extraordinary kind. “In that vast expanse of desert (says he) from W. and to N. W. of us, we saw a number of prodigious pillars of sand at different distances, at times moving with great celerity, at others walking on with a majestic slowness. At intervals we thought they were coming in a very few minutes to overwhelm us; and small quantities of sand did actually more than once reach us. Again they would retreat so as to be almost out of sight; their tops reaching to the very clouds.* There the tops often separated from the bodies; and these, once disjoined, dispersed in the air, and did not appear more. Sometimes they were broken near the middle, as if struck with a large cannon shot. About noon they began to advance with considerable swiftness upon us, the wind being very strong at north. Eleven of them ranged along side of us at about the distance of three miles. The largest of them appeared to me at that distance to be about ten feet diameter. . . . It was in vain to think of flying; the swiftest horse or the fasted sailing ship could be of no use to carry us out of this danger; and the full persuasion of this rivetted me as if to the spot where I stood.” At another time he saw them in much greater number, but of smaller size. They began immediately after sunrise, like a thick wood, and almost darkened the sun. His rays darting through them gave them the appearance of pillars of fire. They now approached to the distance of two miles from our travellers. At another time they appeared beautifully spangled with stars. in Darwin’s Botanic Garden we find a reason assigned for the appearance of these whirlwinds; viz. the impulse of the wind on a long ledge of broken rocks which bound the desert. By these the currents of air which struck their sides were bent and were thus like eddies in a stream of water which falls against oblique obstacles. In the same work we have the following poetical description of them:
“Now o’er their heads the whizzing whirlwinds breathe,
And the live desert pants and heaves beneath;
Ting’d by the crimson sun, vast columns rise
Of eddying sands, and war amid the skies,
In red arcades the billowy plains surround,
And whirling turrets stalk along the ground.”
* N. B. In these sandy deserts, where it never rains, there are no clouds.
Whether the simoom is always preceded by these whirlwinds we know not; but Mr. Bruce mentions an extreme redness of the air, pointed out by his attendant Idris, as the sure presage. His advice was, that all of them, upon the approach of the pernicious blast, should fall upon their faces, with their mouths on the earth, and hold their breath as long as possible, so that they might not inhale the deadly vapour. They soon had occasion to follow this advice; for next day Idris called out to them to fall upon their faces, for the simoom was coming. “I saw (says Mr. Bruce) from the S. E. a haze coming, in colour like the purple part of the rainbow, but not so compressed or thick. It did not occupy twenty yards in breadth, and was about twelve feet high from the ground. It was a kind of blush upon the air, and it moved very rapidly; for I could scarce turn to fall upon the ground, with my face to the northward, when I felt the heat of its current plainly upon my face. We all lay flat on the ground, as if dead, till Idris told us it was blown over. The meteor, or purple haze, which I saw, was indeed passed; but the light air that still blew was of heat sufficient to threaten suffocation. For my part, I felt distinctly in my breast that I had imbibed a part of it; nor was I free of an asthmatic sensation till I had been some months in Italy, at the baths of Poretta, near two years afterwards.” It continued to blow for some time, and in such a manner as entirely to 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.
[66] Est etiam in quibusdam turba inanium verborum, qui dum communem loquendi morem reformidant, ducti specie nitoris, circumeunt omnia, copiosa loquacitate, quæ dicere volunt.
[67] Here Dr. Beddoes, from whose publication this account of Girtanner’s memoir is taken, has the following note: “Dr. Goodwyn had proved this before. Could Dr. Girtanner be ignorant of his experiments?” In justice to myself, however, I must observe that this very doctrine had been published in the Encyclopædia Britannica long before either Dr. Goodwyn or Dr. Girtanner had made any experiments on the subject. It may still be seen under the article Blood, and reasons are there given for supposing that only one part of the oxygen, viz, the elastic part, can be absorbed.