I would have replied sooner, Monsieur and dear colleague, to the letter that you did me the honor of writing me if I hadn't wanted to tell you about the letter that you had me transmit, via l'Abbé Morellet, to M. le Duc de la Vrillière. I had understood, by this, that you wanted me to deliver it to the Minister's own hand, and it is only a few days ago that I was able to see him, and accomplish your commission. He seemed sensitive to this care on your part; you did well then to follow the advice of Chevalier Pringle, and you have seen by my last letter that it was also my advice.

If you were not able to calculate as well in Physics as in Money, or if you were not more learned in the one than the other, you would not have made all the beautiful discoveries that you did. How could you imagine that our French livre is worth 20 English sols? A Frenchman who wished to could easily take advantage of your error. Please know then, Monsieur and dear colleague, that your guinea is worth 24 of our livres, and that the shilling, which is worth a 21st of a guinea, is worth in our money 22 sols + 10 deniers, that is, almost 23 sols. Consequently, the Sterling livre is worth more or less 22 livres and 17 sols, according to the exchange rate, and that therefore the price of the telescope comes to 94 livres and 17 sols of our money. So, since what I gave to M. Du Pont, along with what I paid for the economical lamp and a few other small items, may come to 50 livres, I owe you 44 or about that. For in all of this, I am by no means certain. Neither of us has any more sense than the other, as you say so well. Anyhow, you see by this that far from being indebted to me, it is I who am still indebted to you, not counting what I owe you for the new electrometer. As for your postal charges, please don't speak to me of those trivial things.

M. Walsh showed me M. Henry's electrometer. It can be useful in many situations but I strongly doubt that it can give great precision in the estimation of electrical force. However, I am much obliged for the offers that you have made me regarding this, and consequently I will make use of them if you see fit at the time. Provided however that my errands don't burden you too much.

M. Priestley's experiments provoked interest here, however our best chemists do not consider what he calls fixed air to be a true air. They believe that the properties of this air belong to some foreign particles which are mixed with pure air, and that not belonging to this pure air, they cannot but be the effects of its combination with the foreign elements. Time will tell who is right!

Some chemists from our Academy have come together here to perform some experiments with the molten glass from the Palais Royal, and another glass of the same kind. They have already observed several curious Phenomena, and among others, that despite what M. Homberg had advanced earlier, gold is absolutely invitrifiable or invariant with molten glass. I said at one point that in Physics, one should follow Locke (who wanted it foreseen in his laws for Carolina that one should re-examine them every 50 years to see whether they shouldn't be reformed) that is, fundamental experiments should be repeated from time to time. We go and consider the facts, on others' words, as constant, or as certain, when they are nothing less.

The frigate la Flore, at sea now for a year to test my brother's and other clockmakers' marine chronometers, has just arrived in Brest from its voyage, or at least it is expected there. But there is no certain news yet of how the clocks worked. As so much pleasure is taken here in saying extraordinary things, word has spread that M. le Comte de Lauragais has become a Quaker. I am not sure if your Quakers want our Dukes for fellows.

I see by the English Papers that M. Walsh has returned to London. I hope that you will encourage him to publish his experiments on the torpedo fish; he needs you to press him a little, as I think that, happy to have verified the facts for himself, he is no hurry to publish them, and that would be a great loss. I hope you pass on my countless regards to him as well as to the Chevalier Pringle.

Please receive all my thanks, Monsieur and dear colleague, for the Electrometer and amalgama; as well as the renewed assurances of the distinguished sentiments of esteem and attachment that I have devoted to you for life