SIR,--Your letter of August --, was received a few days ago. Of all the departments of science no one seems to have been less advanced for the last hundred years than that of meteorology. The new chemistry indeed has given us a new principle of the generation of rain, by proving water to be a composition of different gases, and has aided our theory of meteoric lights. Electricity stands where Dr. Franklin's early discoveries placed it, except with its new modification of galvanism. But the phenomena of snow, hail, halo, aurora borealis, haze, looming, &c., are as yet very imperfectly understood. I am myself an empiric in natural philosophy, suffering my faith to go no further than my facts. I am pleased, however, to see the efforts of hypothetical speculation, because by the collisions of different hypotheses, truth may be elicited and science advanced in the end. This sceptical disposition does not permit me to say whether your hypothesis for looming and the floating volumes of warm air occasionally perceived, may or may not be confirmed by future observations. More facts are yet wanting to furnish a solution on which we may rest with confidence. I even doubt as yet whether the looming at sea and at land are governed by the same laws. In this state of uncertainty, I cannot presume either to advise or discourage the publication of your essay. This must depend on circumstances of which you must be abler to judge yourself, and therefore I return the paper as requested, with assurances of my great respect. TO MR. CHILES TERRIL. MONTICELLO, September 25, 1822.