Your kind favor of the 24th. Ult. left for me in Letetia-Court I receiv’d and thank you Sir. I hinted in my first Letter that the Russians had a method of burning their wood for making Pot ash in Kilns, but did not know in what manner they were constructed. I am enquiering about the large City for an intelegent person of that Country to talk with on the Subject, and should I meet with one I will collect all I can and communicate it, and, if possible, will prevail on him to accompany me to your dwelling. I will now impart a matter which, I flatter myself, merits some attention—the thought has just struck me, it is a method of burning wood to such advantage as to obtain every particle of the ashes, and, without further preface, I beg leave to ask wether Mr. Jefferson has Ever seen the manner in which Colliers make Charcoal? If not, I will inform him, that, their wood is cut to one length and piled up Endways perpendicular to the horizon and when ‘tis all fixed, the whole is carefully Covered with Earth, and, then set fire to at an apperture below, left for that purpose, and great care observed to prevent the flame from breaking out, by adding more dirt occassionally, on the appearance of fire, and by this means Charcoal is made, and why the same mode should not succeed for reducing the wood to ashes, by leaving collatteral vent holes in cross directions, I know not. It appears evident to me that great quantities of ashes might be thus obtained—it might be objected, that the dirt would fall on the ashes and injure them, to this I answer, that great part of it might be shovelled off, ere the ashes were gathered, and suppose a little to be left it can be of no ill consequence, provided due care should be taken to have the Lye Clear ere its Evaporation in the kettles. And now Sir, I will go further with the subject. I am of opinion amazing quantitys of ashes might be made in Caves dug into the sides of hills or mountains, the loftier the better, because the top or Crown will be thicker and better calculated to stand the intense heat. The bigness of the Cave must be commensurate to the quantity of wood intended to be burnt. The Cave I conceive might be made something in the following form, but being a poor draftsman I must Endeavour to Explain my ideas the half Circle represents the opening dug into the hill—the middle line represents a Column of the Earth left not only as a support to the roof, but as a passage for the air and smoke to pass round from No. 1 to No. 2, represented by dotts—both Caves are to be filled with wood, and probably if piled perpendicular might be best—it must be set fire to at No. 1 only, and, consequently, No. 2 would be the draft hole—immagine such a place dug into a hill and the natural roof of it will be conceived. The Cave might be made so large as to admit waggons loaded with wood. Several of them might be prepared in the most convenient places, and such places would last time out of mind, provided the mountain was lofty. Should their be no hilly ground suitable, I see no reason why artificial places might not be made in low grounds by digging Cellers walling them up and arching the oven, and the wood might be thrown in thro an opening left in the top. These Crude hints I have thrown on paper for your more mature consideration & am dear Sir your most huml. Servt.