In attempting to point out any adequate reason for the greater salubrity of one place than another, we are constrained to look to other circumstances than those usually embraced in meteorological enquiries: neither the thermometer, barometer, nor hygrometer, furnishing sufficient data for the purpose.
An investigation into the nature and consistence of the soil—the conditions of its surface—the circumstances attendant upon the exhalations arising therefrom—and, above all, the phenomena resulting from their precipitation; conjoined with careful observations on the daily temperature, pressure, motion, and vapour of the air—will be much more likely to elucidate the object of such an inquiry, than the greatest attention bestowed on the latter mentioned points only.
In a district, therefore, where meteorological observations are instituted for the purpose of ascertaining the causes of local salubrity, it will be necessary to notice whether the general character of the soil is clayey or sandy, and this not only with reference to the immediate spot where they may he carried on, but for some miles around; whether the subsoil is rocky, chalky, clayey, or otherwise, and the contiguous localities well or ill drained; whether, in regard to the surrounding district, the particular spot lies high or low; and whether extensive tracts of meadow or arable land prevail; much or little wood, water, &c.
It is well known that the atmosphere has mingled with it variable quantities of aqueous vapour, and likewise the exhalations arising from the materials exposed on the surface of the earth to the sun; it
