ALTITUDE. 



ALUMINA. 



the polar regions. Baron Humboldt, in his 

 Personal Xurrutive, gives us a similar account 

 of the several zones of vegetation existing in a 

 height of 3730 yards on the ascent of Mount 

 Teneriffe. The first zone is the region of vines, 

 ex lending from the shores of the ocean to a 

 height of from 400 to 600 yards, well culti- 

 vated, and producing date trees, plantains, 

 olives, vines, and wheat. The second zone is 

 the region of laurels, extending from about 

 600 to 1800 yards, producing many plants with 

 showy flowers, and moss and grass beneath. 

 The third zone is the region of pines, com- 

 ni'-ncing at 1920 yards, arid having a breadth 

 nf 8f>0 yards. The fourth zone is the region 

 Rffamu, or broom, growing to a height of nine 

 or ten feet, and fed on by wild goats. The last 

 zone is the region of grasses, scantily covering 

 the heaps of lava, with eryptogamic plants in- 

 termixed, and the summit of the mountain 

 bare. 



This accounts for the great variety of plants 

 which is often found in no great extent of 

 country; and it may be laid down as a 

 cal axiom, that the more diversified the surface 

 of the country, the richer it will be in spreies, 

 at least in the same latitudes. It accounts, 

 also, for tin- want of correspondence between 

 plants df different countries, though placed in 

 the same latitudes; because the mountains, or 

 ndin-s of mountains, which may be found in 

 the one and not in the other, will produce the 

 greatest possible difference in the character of 

 the genera and species. To this cause we 

 may ascribe the diversity that often actually 

 exists between plants Crowing in the same 

 country and in the. same latitudes; as between 

 those of the north-west and north-east coasts 

 of North America, as also of the south-west 

 and south-east coasts ; the former being more 

 mountainous, the latter more llat. Sometimes 



se sort of difference takes place t 

 the plants of an island and those of th. 

 bouring continent; that is. if the one is ilat and 

 the other mountainous ; hut it tliey are alike 

 in their geographical delineatior, they are 

 generally alike in their vegetable pro,:; 



[Meteorologists grnerally compute, that -as 

 land rises above the level of the sea or tide- 

 water, the temperature of its climate grows 

 colder at the rate of 1 Fahrenheit, for every 

 300 feet or 100 yards of elevation. It has 

 however been found that the decline of tem- 

 perature on rising above the common level of 

 the sea, is less where large tracts of country 

 rise gradually than when the estimate is made 

 either by balloon ascension, or scaling the 

 sides of isolated and precipitous mountains. 

 A striking illustration of this is offered by the 

 ridges and valleys of the great Himmaleh 

 mountains of Southern Asia, where immense 

 tracts, which theory would consign to the 

 dreariness of perpetual congelation, are found 

 richly clothed in vegetation and abounding in 

 vegetable and animal life. At the village of 

 Zonching, 14,700 feet above the level of the 

 sea, in lat. 31 36 N. Mr. Colebrook found 

 flocks of sheep browsing on verdant hills ; and 

 at the village of Pui, at about the same eleva- 

 tion, there are produced, according to Captain 

 Gerard, the most luxuriant crops of barley, 



wheat, and turnips, whilst a little lower the 

 ground is covered with vineyards, groves of 

 apricots, and many aromatic plants. 



The ejit-cts of gradual elevation in lessening 

 the falling oil" of temperature, is manifested 

 upon a moderate scale in our own country. 

 The [annual] mean temperature of Eastport, 

 Me., for example, is 42.95, whilst that of Fort 

 Snelling in the same latitude, but far in the 

 interior, with an elevation of some 600 or 800 

 feet above the sea, is 2.88 higher, namely, 

 45 .83, instead of being two or three degrees 

 colder, to correspond with the law of eleva- 

 tion. (Amer. Med. Jmir. July, 1842.)] 



ALUM (Lat. Ahimen}. "The sulphate of 

 alumina and potash of the chemist, [or com- 

 mon alum], is composed, according to the ana- 

 lyse of Ut-r/elius (Ann. de Chim. 82 258), of 



Sulphuric arul 34"23 



Alumina 1086 



P..1 981 



Wat.r 4500 



9990 



In veterinary practice, alum in powder is 



axes used externally for destroying 



CCS, arresting bleeding, &c. 



A iKiii-. very finely powdered, is occasionally 



blown thrpugh a quill into the eye for the pur- 



i removing specks of long standing. 



Alum In! inn is prepared by dissolving from 

 six to eight drachms of alum powder in two 

 pints cf water. This forms an inexpensive 

 and tolerably efficacious application for mild 

 '('grease, cracks in the heels of horses, 

 and Tor superficial sores of all kinds. It should 

 not be used till the surrounding inflammation 

 has been subdued by time or proper remedies. 

 In its weakest state, the alum lotion is service- 

 able in the cankered ear of dogs, and wounds 

 or ul'-crs of the mouth in any animal. 



A /urn ointment is composed of one drachm 

 of the p..\vder to one ounce each of turpentine 

 and hog's lard, incorporated by heating. This 

 supplies the place of the lotion when the sores 

 are apt to become dry and hard. It is, how- 

 <.!, very little used. 



Burnt uhtm is made by boiling a solid piece 

 of the salt on an iron plate over a fire till it 

 becomes quite dry and white, taking care not 

 to make the heat so strong as to decompose it. 

 This, in powder, is sometimes used for specks 

 in the eye. (Miller's Dictionary.} 



ALUMINA. The pure earth of clay, was so 

 named from having been obtained in a state 

 of the greatest purity from alum, in which 

 salt it exists combined with sulphuric acid, 

 and potash. This earth when pure has but 

 little taste, and no smell. The earthy smell 

 which clay emits when breathed upon, is 

 owing to the presence of oxide of iron. Its 

 specific gravity is 2-00. When heated it parts 

 with a portion of water, and its bulk is consi- 

 derably diminished. Hence most day lands 

 are apt to crack, by their contraction in dry 

 weather. There is little doubt, from the expe- 

 riments of Davy, but that alumina is the oxide 

 of a metal, which has been denominated 

 aluminum, although he did not succeed in pro- 

 curing it in a separate state. 



Of all the earths alumina is found in plants 

 in the smallest proportions, 32 ounces of the 

 o2 77 



