"I add only a word, in finishing; and that is, that it appears Mr. Leibnitz had a theory of Action, perhaps much more extensive than one would suspect at present. There is a Letter written by him to Mr. Hermann [an ancient mathematical sage at Basel], where he uses these expressions: 'Action, is not what you think; the consideration of Time enters into it; Action is as the product of the mass by the space and the velocity, or as the time by the VIS VIVA. I have remarked that in the modifications of motion, the action becomes usually a maximum or a minimum:--and from this there might several propositions of great consequence be deduced. It might serve to determine the curves described by bodies under attraction to one or more centres. I had meant to treat of these things in the Second Part of my DYNAMIQUE; which I suppressed, the reception of the First, by prejudice in many quarters, having disgusted me.'" [MAUPERTUISIANA, No. ii. 22 (from--Acta Eruditorum,--ubi supra). In MAUPERTUISIANA, No. iv. 166, is the whole Letter, "Hanover, 16th October, 1707;" no ADDRESS left, judged to be to Hermann. MAUPERTUISIANA (Hamburg, 1753) is a mere Bookseller's or even Bookbinder's Farrago, with printed TITLE-PAGE and LIST, of the chief Pamphlets which had appeared on this Business (sixteen by count, various type, all 8vo size, in my copy). Of which only No. ii. (Konig's APPEL AU PUBLIC) and No. iv. (2d edition of said APPEL, with APPENDIX OF CORRESPONDENCE) are illuminative to read.] Your Minimum of Action, it would appear, then, is in some cases a Maximum; nothing can be said but that, in every case it is EITHER a Maximum or Minimum. What a stroke for our LAW OF THRIFT, the "at last conclusive Proof" of an Intelligent Creator, as the Perpetual President had fancied it!"So-ho, what is this! My Discovery an Error? And Leibnitz discovered it, so far as true?"--