# Letter from Newton to John Collins, dated 13 July 1672

Stoake. July 12|3|^{th}. 1672.

S^{r}

I think I told you |y^{t}| I had altered my resolution of printing my Dioptrick Lectures. And for y^{e} exercise about Infinite series I am not yet resolved, not knowing when I shall proceed to finish it. I will inquire of some of o^{r} Booksellers whether they will purchase M^{r} Pitts his copy of Kinckhuysen & if not I will send it you. In the meane while I would know whether M^{r} Pitts thinks it will be more advantageous to prind|t| y^{e} Author without alteration, or to insert those notes w^{ch} you formerly saw, y^{t} I may according send them w^{th} y^{e} Copy or detain them. M^{r} Gregorys Problem of finding y^{e} solidity of the second segments of a Sphere & yo^{rs} of finding the surfaces of i{illeg}|n|clined round solids may be solved divers ways by infinite sed|r|ies, as I find by considering them in generall, but I foresee the calculations are intricate & unpleasant w^{ch} has made me neglect them, not thinking them worth transmitting to you. If I ever applyed Gund|t|ers Sector to the resolving of affected æquations it hath now slipt out of my memory. Possibly it might be Gunters line w^{ch} being set upon 3 or 4 severall rulers is of ready use for finding y^{e} 2 or 3 first figures of any affected æquatio{n} but there is no difficulty in y^{e} invention. And if it be y^{e} same w^{ch} you meane, you may command it. The way of resolving Problems \æquations/ of 5 or 6 dimensions, by a locus linearis was I beleive by the intersection of that & a Conick Section, something after the manner y^{t} Des-Cartes hath done it, but more conveniently in my opinion, because the same locus linearis once described will serve for y^{e} resolving of all Problems \Equations of those dimensions/. And as I remember the calculations to y^{t} intent are shorter & lesse intricate. I am at present in Northampton shire whither your letter was sent to me from Cambridge: But hope within 8 or 9 days to be at Cambridge to receive what you may send thither if you shall have occasion to write to

Yo^{r} humble & much

obliged Servant

Newton.

There are three more of M^{r} Kersies Bookes of Algebra desired in Cambridg for w^{ch} at p^{r}sent you may subscribe my name.