I am sorry it is not in my power to begin immediately the course of observations you proposed in your last letter. I have not a thermometer even, at present, but shall provide myself directly with one, and as soon as possible with a Barometer. The addition of the Meteorological phaenomena, observations with respect to the migration of birds, and the changes in plants ought to render it a pleasing task to the Philosopher, the Sportsman and the Farmer, equally. Had it been more the custom for men of the two latter classes to note down what so strongly attracted their attention, we would have been better acquainted with those parts of Nat. History, without the assistance of Speculative ability. The difference of climates is undoubtedly produced by the difference of elevation above the common Surface of the Earth, without much regard I believe to the direction of the rays of the Sun, but the frequent alteration of temperature in any particular climate seem to prevail generally throughout the same Hemisphere, and of course to be occasioned by some change of the situation of the Earth with respect to the Sun. Perhaps warm and cold weather in the contrary seasons may be occasioned by the retrograde motion of the Earth in her Orbit: I suppose her motions are as irregular as those of the other planets. If such Diaries as you propose were kept in several different countries, it might be ascertained whether these sudden changes were really general in the Northern Hemisphere. I fancy they would be found to be much more so, than they are thought to be.

I shall be much obliged to you, if it should in any manner come in your way without a particular enquiry to give me an account of the quantity of coal which is imported into the United States. That article pays a small duty I believe which will render it easy to ascertain the quantity. The Strata in Virginia are as frequent, much more productive, and may be worked to as great advantage as any in the world. The quality of the coal I fancy is excellent for it contains a greater quantity of inflammable substance than any I have ever met with. It is unlucky that the importation had not been so much discouraged as to induce moneyed men to lay out their capitals that way. I am Dear Sir your most obed. Servt.