Boreas; Aparctias; Septentrion North Degrees. O planation of the Temple of 45 the Winds at 90 Athens, in Vi135 truvius, 1. 1. 180 cap. 6. Arist. Meteor. 1. II. 225 cap. 6. Pliny 270 11.262. Aulus 315 Gellius II. 42, &c. South South-West West North-West North 360 In reckoning from the north round the compass, we can thus better understand the arrangement. Navigators reckon by quarters of circles only, in going from the north to east, or to west, and the same from the south to east, or to west, Professor Leslie, to whose liberality the publishers are indebted for the following tables, (XIII. and XIV.) says, "I have been able, after a delicate and patient research, to fix the law which connects the decrease of temperature with the altitude. If B and b denote the barometric pressure at the lower and upper stations; then will will()25 express, on the centigrade scale, the diminution of heat in ascent. Hence, for any given latitude, that precise point of elevation may be found, at which eternal frost prevails. Put x = and t the standard tempe b B dratic equation being resolved, gives the relative elasticity of the air at the limit of congelation, whence the corresponding height is determined. From these data the following table has been calculated. This table (XIII.) will facilitate the approximation to the altitude of any place, which is inferred either from its mean temperature, or its depth below the boundary of perpetual congelation. The decrements of heat at equal ascents are not altogether uni form, but advance more rapidly in the higher regions of the atmosphere. At moderate elevations, however, it will be sufficiently near the truth, to assume the law of equable progression, allowing in this climate (56° N.) one degree of cold by Fahrenheit's scale for every ninety yards of ascent, and for every hundred yards in the tropical regions. Dr. Francis Buchanan Hamilton found the temperature of a spring at Chitlong, in the Lesser Valley of Nepal, to be 14°. 7 centigrade. But the mean temperature in the parallel of 27° 38 being 22. 8, the density of the atmosphere corresponding to difference 8.1, is 8510, which gives 4500 feet for the corrected altitude. |