Sir,--I cannot gather from your "Notes" that scientific archæology is included in your plan, nor yet, on the other hand, any indications of its exclusion. Science, however, and especially mathematical science, has its archæology; and many doubtful points of great importance are amongst the "vexed questions" that can only be cleared up by _documentary evidence_. That evidence is more likely to be found mixed up amongst the masses of papers belonging to systematic collectors than amongst the papers of mere mathematicians--amongst men who never destroy a paper because they have no present use for it, or because the subject does not come within the range of their researches, than amongst men who value nothing but a "new theorem" or "an improved solution." As a general rule I have always habituated myself to preserve every scrap of paper of any remote (and indeed recent) period, that had the appearance of being written by a literary man, whether I {133} knew the hand, or understood the circumstance to which it referred, or not. Such papers, whether we understand them or not, have a _possible value_ to others; and indeed, as my collections have always been at the service of my friends, very few indeed have been left in my hands, and those, probably, of no material value. I wish this system were generally adopted. Papers, occasionally of great historical importance, and very often of archæological interest, would thus be preserved, and, what is more, _used_, as they would thus generally find their way into the right hands. There are, I fancy, few classes of papers that would be so little likely to interest archæologists in general, as those relating to mathematics; and yet such are not unlikely to fall in their way, often and largely, if they would take the trouble to secure them. I will give an example or two, indicating the kind of papers which are desiderata to the mathematical historian.