REID'S CHEMISTRY OF NATURE.
This is a well-executed and useful little work. It is addressed to the general reader ; and gives a view of the principles of chemical science, awl of their province in explaining the plicenemena of the material world. The nature and properties of those great agents air and water are fully examined ; and there is an excellent account of the chemical laws of geology, and of animal and vegetable physioloey. Clearness and simplicity of style, and great felicity of illustration. are the characteristics of the book. Mr. Rein is the Lecturer on Chemistry to the Glasgow High School and the Glaseow Mechanics' Institution. In his preface he expresses his satisfaction that scientific instruction is beginning to be adupted as an essential part of the course in elementary SC11001S; and adds—" In many private academies the system has been permanently established, and is attended with greet success. The new High Scheel of Liverpool includes a philosophical de- partment ; and in the High School of Glasgow a chemical class has been instituted. No doubt, in course of time, the Univer- sities will introduce all the sciences into the curriculum for their degree of Master of Arts, and render it worthy of the present ad- vanced state of knowledge." No doubt they will, but not till they cannot help it. They will take care to he last in the race of im- provement.
The following extracts will show the author's popular manner of treating a scientific subject. The last of them is merely a quo- tation from another writer ; but it is curious and striking. We suppose that the Valley of Death has given rise to the fable of the Upas tree, which has been described as growing in precisely such a locality.
PROOFS THAT THERE IS SUCH A SCIISTANCE AS THE AIR.
At first we might suppose the air not to be a substance or body ; we walk in it and move every limb without any feeling indicating the presence of any thing. We cannot see nor touch it ; it has no taste or smell. On a calm day one ought be apt to say, on looking on a buibling at a distance, that there is nothing between him and the building—that the space between IS empty; but let hun run, or be on the top of a coach going very fast, or even move the hand briskly, he will then have a feeling of some impreoion on his lice or hand, like that of somo light substance striking him, or like a gentle breeze. If, while running, he hold an open umbrella behind him, he will feel something resisting the advance of the umbrella, and rendering the exertion of force on his part necessary to pull it onwards, while no such force will be required to carry the umbrella closed, like a walking-stick, in the hand. There must be some substance present which causes the impression on the face or hand, and re4sts the open umbrella while advancing. Tilk substance is the air : it is in- visible, so that we see nothing in the space which it occupies; and we do not feel it on a calm day when we arc moving slowly, because it is so extremely light, and its particles strike upon the face on gently and at comparatively long intervals. But when we move fast the it:inn:les of air strike with a greater impetus, and hence produce a decided impression. When we attempt to draw the open umbrella along, we feel a great resistance, because the umbrella has to push sue:: a Ir:rge quaraity of air before it ; when the umbrella is eloscd, it has to push out oi itti way a much less quantity of air, hence less force is required. If we reflect that there is really no reason why matter should be very heavy (indeed, there is a gas sixteen times lighter than air), and no reason why it must always be visible, we shall have little difficulty iu conceiving that air is 0 substance or body as well as water or iron. Nothing shows better that air is a substance than the nature of wind. Winffi—whether a gentle breeze that is scarcely felt upon the cheek, and is insufficient to swell wit the canvas of a sailing-ve,sel, a brisk gale, communicating a strong impulse to the sails of a ship, and driving it along at the rate of many miles an hour, or a hurricane tearing lip trees by the roots, cohverting the surface of the wean into raging billows, and hurrying every thing before it in its progre,s,---is nothing but air in a Stat.; of motion ; in the first case moving very slowly, in the last moving with almost incredible veh city (at the rate of scores of miles hourly) ; and it is its velocity to which it owes its force. When moving slowly it is scarcely felt, just as a leaden ball might be thrown so gently at a board as to leave not the slightest impression, while the 611lb:ball, if olischarged with explosive violence from a musket, would pmetrate the hardest oak. The phenomena of clouds or a balloon floating in the air, or of birds flying. also point out that it is a material substance. They rest upon the air irk the same way IN a ship does on the sun, face of water. A person looking into a room III which nothing can be seen but the walls, would he apt to say. there is nothing in it ; but there PI air, and althomffi he does nit see it, the room is completely filled with it, so much so, that if he walk into it he drives out so much of the air at the mommt in which he enters, Other proofs that the air is a substance or body, will be given as we proceed, such as its weight and pressure, and ite colour.
THE VALLEY OF DEATH.
'There are two remarkable instances in nature of a corrupted state of the atmosphere, by which it is unable to support animal life—the Grotto del Cane (grotto of the dog), in Italy, and the Valley of Death, in the island of devil; both
depending on the presence of carbonic acid in the atmosphere in unusually large
proportion. The latter has been described by Mr. Loudon in No. 2:1 of the Edinburgh Philosophical Journal ; from which the following extracts are made. "Baler Bd July 'MO.—This evening, while walking round the village with the Patteh (native chief,) he told me that there was a valley only three miles from Balm., that no person could approach without forfeiting their lives, and that the skeletons of human beings and all sorts of beasts and bird.,, covered the bottom of the valley. We took with us two dogs and SOIEC fowls, to try expe- riments in this poisonous hollow. When within a few yards of the valley, we experienced a strong, nauseoue, suffiwating smell, but, on coming close to the edge, this disagreeable smell left M. We were now all lost in aetonieliment it the awful scene before us. The valley appeared to be about half a-mee in circum- ference, oval, and the depth from :30 to 33 feet, the bottom quite vege- tation—sonie very large, in appearance, river-stones, ;Ind the whole covered with the skeletons of human beings, tigers, pigs, deer, peacock., and all sorts of birds. We could not perceive any vapour or any opening in the ground, which la.t appeared to be of a hard sandy substance. The sides of the val,ey from the top to the bottom are covered with tree, shrubs, &e. It was now proposcd by one of the party to enter the valley ; but at the spot where we were, this was difficult, at least for me, as one false step would have brought us to eternity, as no assistance could be given. We lighted our cigars, and, with the aeeietance of a bamboo, we went down within eighteen feet of the bettone Here we did not experience any difficulty in breathing, but an offensive eruseene smell annoyed us. We now faeteued a dog to the end of a bemboo, eighteen feet long, mid sel■t him in ; we hail our watchee in our hands, and in foui teen seconds he tell on hie back, did not move his limbs, or look around, but continued to breathe eighteen minutes. We then sent in another, or rather he got loose front the bamboo, but walked in to where the other dog was lying: lie then stood quite still, and in ten seconds he fell on his face, and never moved his limbs afterwards he continued to breathe for seven minutes. We now tried a fowl, which died in one minute and a half. We threw in another, which died before touching the ground. During these expetimente we experienced a heavy shower of rain ; but we were so interested by the awful scene before us, that we did not care for
getting wet. On the opposite side, near a large stone, was the skeleton of a human being, who must have perished on his back, with the right total under the head : ?tom being exposed to the weather, the bones were bleached as white as ivory. I was anxious to procure this skeleton, but any attempt to get at it would have ben madness." " The human skeletons are supposed to have been rebels, who had been pursued from the main road, and taken refuge in the differ- ent valleys, as a wanderer cannot know his danger till he is in the valley, and when mice there, one has not the power or presence of mind to return."
It does not seem that any attempts were made to colleet some of tl:c air in the valley bw examination, but there is every reason to believe th it it consists of, or contains a large proportion of carbonic acid,—a gas which is known to be abundant in volcanic countries ; while the effects on the animals sent in to the valley resemble those which would be produced in .an atmosphere of this gas
Carbonic acid gas is very heavy, and hence readily accumulates in any low situation where it may be poured into the atmosphere. In the present case, aud in the Grotto del Cane, (a cave in which similar plicenomena are oleierved in the strata of air next the ground,) it may be supposed that the carbonic acid gas is produced in the interior of the earth by some volcanic actions, which it is known arecoutinually going on at no great distance, and that by fissures in the ground it passes through to the surface, where, front being surrounded by the sides of the valley, and thus excluded from the action of the winds, it accumn- lutes, and mixes very slowly with the general mass of the atmosphere,
Previous page
