My last letter to you was of the 13th. of August last. As you seem willing to accept of the crums of science on which we are subsisting here, it is with pleasure I continue to hand them on to you in proportion as they are dealt out.  Herschel’s volcano in the moon you have doubtless heard of, and placed among the other vagaries of a head which seems not organised for sound induction. The wildness of the theories hitherto proposed by him, on his own discoveries, seems to authorize us to consider his merit as that of a good Optician only. You know also that Doctor Ingen-housz had discovered, as he supposed, from experiment, that vegetation might be promoted by occasioning streams of the electrical fluid to pass through a plant, and that other Physicians had received and confirmed his theory. He now however retracts it, and finds, by more decisive experiments, that the electrical fluid can neither forward nor retard vegetation. Uncorrected still of the rage of drawing general conclusions from partial and equivocal observations, he hazards the opinion that light promotes vegetation. I have heretofore supposed from observation that light affects the colour of living bodies, whether vegetable or animal; but that either the one or the other receive nutriment from that fluid must be permitted to be doubted of till better confirmed by observation. It is always better to have no ideas than false ones; to believe nothing, than to believe what is wrong. In my mind, theories are more easily demolished than rebuilt. An Abbé here has shaken, if not destroyed, the theory of de Dominis, Descartes and Newton for explaining the phaenomenon of the rainbow. According to that theory, you know, a cone of rays issuing from the sun and falling on a cloud in the opposite part of the heavens, is reflected back in the form of a smaller cone, the apex of which is the eye of the observer: thus.
(a) the sun. (b) (c) the diameter of the rainbow (d) the eye of the observer. So that (d) the eye of the observer must be in the axis of both cones, and equally distant from every part of the bow. But he observes that he has repeatedly seen bows the one end of which has been very near to him, and the other at a great distance. I have often seen the same thing myself. I recollect well to have seen more than once1 the end of a rainbow between myself and a house, or between myself and a bank not twenty yards distant, and this repeatedly. But I never saw, what he sais he has seen, different rainbows at the same time intersecting each other. I never saw coexistent bows which were not concentric also.—Again, according to the theory, if the sun is in the horizon, the horizon intercepts the lower half of the bow, from (e) to (c). If above the horizon, that intercepts more than the half, in proportion. So that generally the bow is less than a semicircle and never more. He says he has seen it more than a semicircle. I have often seen a leg of the bow below my level. My situation at Monticello admitted this, because there is a mountain there in the opposite direction of the afternoon’s sun, the valley between which and Monticello is 500 feet deep. I have seen a leg of a rainbow plunge down on the river running through that valley. But I do not recollect to have remarked at any time that the bow was of more than half a circle. It appears to me that these facts demolish the Newtonian hypothesis but they do not support that erected in it’s stead by the Abbé. He supposes a cloud between the sun and observer, and that through some opening in that cloud the rays pass and form an Iris on the opposite part of the heavens, just as a ray passing through a hole in the shutter of a darkened room, and falling on a prism there, forms the prismatic colours on the opposite wall. According to this we might see bows of more than the half circle as often as of less. A thousand other objections occur to this hypothesis, which need not be suggested to you. The result is that we are wiser than we were, by having an error the less in our catalogue; but the blank occasioned by it must remain for some happier hypothesist to fill up.

The dispute about the conversion and reconversion of water and air is still stoutly kept up. The contradictory experiments of Chemists2 leave us at liberty to conclude what we please. My conclusion is that art has not yet invented sufficient aids to enable such subtle bodies to make a well defined impression on organs as blunt as ours: that it is laudable to encourage investigation, but to hold back conclusion. Speaking one day with Monsieur de Buffon on the present ardor of chemical enquiry, he affected to consider chemistry but as cookery, and to place the toils of the laboratory on a footing with those of the kitchen. I think it on the contrary among the most useful of sciences, and big with future discoveries for the utility and safety of the human race. It is yet indeed a mere embryon. It’s principles are contested. Experiments seem contradictory: their subjects are so minute as to escape our senses; and their result too fallacious to satisfy the mind. It is probably an age too soon to propose the establishment of system. The attempt therefore of Lavoisier to reform the Chemical nomenclature is premature. One single experiment may destroy the whole filiation of his terms, and his string of Sulfates, Sulfites, and Sulfures may have served no other end than to have retarded the progress of the science by a jargon from the confusion of which time will be requisite to extricate us. Accordingly it is not likely to be admitted generally.

You are acquainted with the properties of the composition of nitre, salt of tartar and sulphur called Pulvis fulminens. Of this the explosion is produced by heat alone. Monsieur Bertholet by dissolving silver in the nitrous acid, precipitating it with lime water, and drying the precipitate on Ammoniac has discovered a powder which fulminates most powerfully on coming into contact with any substance whatever. Once made it cannot be touched. It cannot be put into a bottle, but must remain in the capsula where dried.—The property of the Spathic acid to corrode flinty substances, has been lately applied by a M. Puymaurin, of Toulouse, to engrave on glass, as artists engrave on copper with aquafortis.—M. de la Place has discovered that the secular acceleration and retardation of the moon’s motion is occasioned by the action of the sun, in proportion as his eccentricity changes, or, in other words, as the orbit of the earth increases or diminishes. So that this irregularity is now perfectly calculable.—Having seen announced in a gazette that some person had found in a library of Sicily an Arabic translation of Livy, which was thought to be complete, I got the Chargé des affaires of Naples here to write to Naples to enquire into the fact. He obtained in answer that an Arabic translation was found, and that it would restore to us 17 of the books lost, to wit, from the 60th. to the 77th. inclusive: that it was in possession of an Abbe Vella at Palermo who, as soon as he shall have finished a work he has on hand, will give us an Italian and perhaps a Latin translation of this Livy. There are persons however, who doubt the truth of this discovery, founding their doubts on some personal circumstance relative to the person who sais he has this translation. I find nevertheless that the Chargé des affaires believes in the discovery, which makes me hope it may be true.

A country man of ours, a Mr. Lediard of Connecticut set out from hence some time ago for St. Petersburgh, to go thence to Kamschatka, thence to cross over to the Western coast of America, and penetrate through the continent to our side of it. He had got within a few days journey of Kamschatka, when he was arrested by order of the empress of Russia, sent back and turned adrift in Poland. He went to London, engaged under the auspices of a private society formed there for pushing discoveries into Africa, passed by this place, which he left a few days ago for Marseilles, where he will embark for Alexandria and Grand Cairo, thence explore the Nile to it’s source, cross to the head of the Niger, and descend that to it’s mouth. He promises me, if he escapes through this journey, he will go to Kentuckey and endeavour to penetrate Westwardly from thence to the South sea.

The death of M. de Buffon you have heard long ago. I do not know whether we shall have any thing posthumous of his.

As to political news, this country is making it’s way to a good constitution. The only danger is they may press so fast as to produce an appeal to arms, which might have an unfavorable issue for them. As yet that appeal is not made. Perhaps the war which seems to be spreading from nation to nation may reach them. This would ensure the calling of the states general, and this, as is supposed, the establishment of a constitution.  I have the honor to be with sentiments of sincere esteem & respect, Dear Sir Your friend & servant,