I have duly recieved your favor of Apr. 26. in which you are pleased to ask my opinion on the subject of the arrangement of libraries. I shall communicate with pleasure what occurs to me on it. two methods offer themselves. the one Alphabetical, the other according to the subject of the book. the former is very unsatisfactory, because of the medley it presents to the mind, the difficulty sometimes of recollecting an author’s name, and the greater difficulty, where the name is not given of selecting the word in the title which shall determine it’s Alphabetical place. the arrangement according to subject is far preferable, altho’ sometimes presenting difficulty also. for it is often doubtful to what particular subject a book should be ascribed. this is remarkably the case with books of travels, which often blend together the geography, natural history, civil history, agriculture, manufactures, commerce, arts, occupations, manners Etc. of a country, so as to render it difficult to say to which they chiefly relate. others again are polygraphical in their nature, as Encyclopedias, Magazines Etc. yet on the whole I have preferred arrangement according to subject; because of the peculiar satisfaction, when we wish to consider a particular one, of seeing at a glance the books which have been written on it, and selecting those from which we expect most readily the information we seek. on this principle the arrangement of my library was formed, Of the Advancement and Proficiencie of Learning: or the Partitions of Sciences and I took the basis of it’s distribution from Ld Bacon’s table of science, modifying it to the changes in scientific pursuits which have taken place since his time, and to the greater or less extent of reading in the several sciences which I proposed to myself. thus the law having been my profession, and politics the occupation to which the circumstances of the times in which I have lived called my particular attention, my provision of books in these lines, and in those most nearly connected with them, was more copious, and required in particular instances subdivisions into sections and paragraphs, while other subjects, of which general views only were contemplated, are thrown into masses.

a physician or theologist would have modified differently the chapters sections and paragraphs of a library adapted to their particular pursuits.

You will recieve my library arranged very perfectly in the order observed in the Catalogue, which I have sent with it. in placing the books on their shelves, I have generally, but not always, collocated distinctly the folios, 4tos 8vos & 12mos placing with the last all smaller sizes. on every book is a label, indicating the chapter of the catalogue to which it belongs, and the order it holds among those of the same format. so that, altho’ the Nos seem confused on the catalogue, they are consecutive on the volumes as they stand on their shelves & indicate at once the place they occupy there. Mr Millegan, in packing them has preserved their arrangement so exactly, in their respective presses, that on setting the presses up on end, he will be able readily to replace them in the order corresponding with the catalogue, and thus save you the immense labor which their re-arrangement would otherwise require.

To give to my catalogue the conveniences of the Alphabetical arrangement, I have made at the end an Alphabet of Authors’ names, and have noted the chapter, or chapters, in which the name will be found. where it occurs several times in the same chapter it is indicated by one or more1 perpendicular scores, thus | | | |. according to the number of times it will be found in the chapter. where a book bears no author’s name, I have selected, in it’s title, some leading word for denoting it Alphabetically. this member of the catalogue would be more perfect if, instead of the score, the number on the book were particularly noted. this could not be done when I made the catalogue, because no label of numbers had then been put on the books. that alteration can now be readily made, and would add greatly to the convenient use of the Catalogue. I gave to mr Millegan a note of three folio volumes of the laws of Virginia belonging to the library which being in known hands, will be certainly recovered, and shall be forwarded to you. one is a MS. volume from which a printed copy is now preparing for publication.

This statement meets, I believe, all the enquiries of your letter, and where it is not sufficiently minute, mr Millegan, from his necessary acquaintance with the arrangement, will be able to supply the smaller details. Accept the assurances of my respect and consideration.

Th: Jefferson