Cambridge: University Press, 1906. First Edition. paperback. No. 4 in series of Cambridge Tracts in Mathematics and Mathematical Physics, edited by J.G. Leathem & E.T. Whittaker. Illustrated with diagrams. viii, 64pp. Slim 8vo, original printed paper wrappers (spine darkened but otherwise wraps are only slightly toned; small ink smudge on cover and neatly inked signature on half title, otherwise clean). Cambridge: University Press, 1906. First edition. very good(+).
An excellent copy of this very scarce tract, likely his second published work, after The Treatise on Universal Algebra, in 1898.