This method of measuring elevations on the sur face of the globe is, therefore, capable of great im provement, and might be employed with advantage in a variety of cases where observations with the ba rometer are not easily obtained. Its application would be most important to physical geography, in ascer taining the capital points for tracing the outline of the profile or vertical section of any country. The common maps, which exhibit mere superficial ex tension, are quite insufficient to represent the great features of nature, since the climate and productions of any place depend as much on its elevation above the sea as its latitude. Scientific travellers have ac cordingly turned their attention of late years to the framing of vertical sections. As a specimen, we give in fig. 22, from Humboldt's Geography of Plants, a section across the American Continent, one of the best and most interesting that has yet appeared. It consists, in fact, of four combined sections, tra versing through an extent of 425 miles. The line begins at Acapulco on the shore of the Pacific Ocean, and runs 195 miles, about a point of the compass towards the East of North, to the city of Mexico; then 80 miles, a point to the South of East, to La Puebla de los Angeles ; again it holds a North-East direction of 70 miles, to the Cruz Blanca ; and finally bends 80 miles East by South, to Vera Cruz, on the coast of the Atlantic. A scale of altitudes is annexed, which shows the vast elevation of the table-land of Mexico. An attempt is likewise made in this profile to give some idea of the geological structure of 'the external crust. Limestone is represented by straight lines slightly inclined from the horizontal position : Basalt, by straight lines slightly reclined from the perpendicular : Porphyry, by waved lines somewhat reclined : Granite, by confused hatches : Amygdaloid, by confused points.
By this mode of 'distant levelling, a very interest ing discovery, in another quarter of our globe, has been recently made by Engelhardt and Parrot, two Prussian travellers. They proceeded, on the 13th July 1814, from the mouth of the Kuban, at the island of Taman, on the Black Sea ; and, examin ing carefully every day the state of the barometer, they advanced with fifty-one observations, the dis tance of 990 wersts, or 711 English miles, to the mouth of the Terek, on the margin of the Caspian Sea. Similar observations were repeated and mul tiplied on their return. From a diligent comparison
of the whole, it follows that the Caspian is 334 Eng lish feet below the level of the Black Sea. That the . Caspian really occupies a lower level than the Ocean, had been suspected before, from a comparison of some registers of barometers kept at St Petersburg, and on the borders of that inland sea; but the last observation places the question beyond all doubt. It farther appears, that within 250 wersts, or 189 miles, of the Caspian, the country is already depress ed to the level of the Ocean, leaving, therefore, an immense bason, from which the waters are supposed to have retired by a subterranean percolation. (D.) whom is generally a military man. The mode of writing letters in this public department is deserving of notice and imitation, as securing despatch and ac curacy. A sheet of paper being folded in the mid dle, officers of the department, who address the bar rack-office, write their letters on the left side ; and, along with the original letter, send a duplicate in the same form, and signed also. On the blank side of • the duplicate is written the official answer from the barrack-office which is sent; and, on the original let ter, which is preserved in the office, is copied the an swer: each party has thus an exact copy of the whole correspondence.
As it frequently happened, that it was absolutely necessary to build barracks on an emergency, when there was no time to summon a jury to value the land before the commencement of the building, and as most persons were averse to have barracks near their dwelling-houses, or even on their property, Government was often obliged to pay an extrava gant price for the land which they needed for their erection • in order to remedy this evil, it was provid ed by the act, usually called the defence act, 43d Geo. III. cap. 55, that Justices of the Peace might put any general officer into the possession of such ground as be might deem fit for the erection of barracks ;—the value of it to he settled afterwards by a jury ;—provided, however, the necessity for such ground was certified by the Lord-Lieutenant, or two Deputy-Lieutenants of the county.
Barracks throughout the country are more imme diately under the management and care of the assist ant-barrack-masters-general, and the resident bar rack-masters ; the former are attached to districts; the latter to particular barracks. The following are the districts in Great Britain ;