Birds, p. 353), the avifauna of Madagascar is not entirely composed of such **singularities** as these.

There are other infinite **singularities** of detail; but the above are more than sufficient to establish the point.

For example, in the curve for gold-aluminium, ignoring minor **singularities**, we find two intermediate summits, one at the percentage Au 2 A1, and another at the percentage AuAl 2.

Among his most remarkable works may be mentioned his ten memoirs on quantics, commenced in 1854 and completed in 1878; his creation of the theory of matrices; his researches on the theory of groups; his memoir on abstract geometry, a subject which he created; his introduction into geometry of the "absolute"; his researches on the higher **singularities** of curves and surfaces; the classification of cubic curves; additions to the theories of rational transformation and correspondence; the theory of the twenty-seven lines that lie on a cubic surface; the theory of elliptic functions; the attraction of ellipsoids; the British Association Reports, 1857 and 1862, on recent progress in general and special theoretical dynamics, and on the secular acceleration of the moon's mean motion.

Allied to the matter just mentioned was Plucker's discovery of the six equations connecting the numbers of **singularities** in algebraical curves (see Curve).

The work falls into two parts, which treat of the asymptotes and **singularities** of algebraical curves respectively; and extensive use is made of the method of counting constants which plays so large a part in modern geometrical researches.