Once Hutton had conceived his columns: “it is evident that the plan must be divided into a great number of parts, perhaps not less than a thousand for each observatory… forming about two thousand such pillars of matter…” With his pillars planned it became apparent that not each one had a spot height within it:
“numerous as these points are, there are evidently many bases in which none at all are contained, nor even near them. The circumstance at first gave me much trouble and dissatisfaction, till I fell upon the following method…”
These snippets appear within the 100 plus pages of Hutton’s calculations, where even the title seems inordinately long and tedious: “An Account of the Calculations made from the Survey and Meafures taken at Schehallien, in order to afcertain the mean Denfity of the Earth”.
Over half the pages are devoted to mathematical tables I struggle to follow, with each reading though I began to see the shape at least of each necessary calculation.
My way of tackling it, is to conceive of it as a cookery book: all the ‘ingredients’ needed to recreate the missing (first contour line) map are there, just I don’t possess the skills to follow the recipe.
However through very good fortune I found my ‘Master Chef’; the head librarian at the Lit and Phil put me in touch with Emeritus Professor of Mathematics Robin Johnson who skilfully number-crunched Hutton’s calculations into a visual format I could follow. Work has begun on recreating the missing map which hopefully will be ready for unveiling at the Great Lines exhibition next month.