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the mountain, which overhangs this village on the north fide, may, by its refleftion, have contributed fomewhat to produce this heat. The dif- ference of temperature of the air at the fea-coaft, or on the Chefapeak bay, and at the AUeghaney, has not been afcertained; but contemporary obfervations, made at Williamfburgh, or in its neighbourhood, and at Monticello, which is on the moft eaftern ridge of the mountains, called the South-weft, where they are interfered by the Rivanna, have furnifhed a ratio by which that difference may in fome degree be conjetSured. Thefe obfervations make the difference between Williamfburgh and the neareft mountains, at the pofition be- fore-mentioned, to be on an average 6% of Farenheits's thermometer. Some al- lowance, however, is to be made for the difference of latitude between thefe two places, the latter being 38"" 8^ 17'^ which ^ is 52^ 22'''' north of the former. By con- temporary obfervations of between five and fix weeks, the averaged and almoft unvaried difference of the heigh th of mer- cury in the barometer, at thofe two places, was .784 of an inch, the atmof- phere at