I took the liberty to trouble you with a line the last post, and being but just able to finish my letter in time, I recollect a mistake in the catalogue of books wanted, which I beg you would rectify as follows,

Vitelliones Optica best edition 1572

Kepler’s Paralipomena in Vitellionem I also very much want De la Hire’s differens Accidents de la vue. But I should think it might be got without a public advertisement. I have already collected from that writer as much as will make a considerable section. I cannot well do without Du Hamel’s History of the French Academy, and tho’ it is inserted among books I have got, it is only in the library at Manchester, and I cannot, without great loss of time, and expence, go and study there. Many other books I foolishly inserted in the catalogue of those I had access to, which are only there, particularly the Petersburg Memoirs which I must absolutely purchase, tho they will cost me, I believe, above £20. I shall give Johnson orders for them this post. I have not yet got Boyle’s Works, and I find a tract of his on colours quoted, but I believe it relates to the chymical production of colours. However it is within my subject, but Johnson, tho’ he has had my order for Shaw’s Boyle several months, has not yet been able to get it.

I have just dispatched the discoveries of Newton and his Contemporaries, and from his time to the present have such a number of Memoirs, dissertations, tracts, and books on the subject of Light and colours to read, compare, and digest, as, I think, would make any person not practised in the business of arrangement, absolutely despair: Till I had actually taken a list of them, I did not think there had been a tenth or a twentieth part so much upon the subject. And other subjects, I see, will be much times more embarassing than this.

If you be obliged to advertise for the books I think it would be better not to mention my name, but only say A Person being employed &. I am, with the greatest respect Dear Sir your friend and Servant