ISOCHRONISM—JOHNSON. 
106 
Isochronism: of circular hodograph, in, 262—5. 
Isomers: Mathematical theory of, ix, 202—4. 
Isoparametric Lines: and planet’s orbit, vn, 467. 
Isoperimetrical Problem : vn, 263. 
Isothermals: of Meyer, xm, 175. 
Jacobi, K. G. J.: theory of algebraic curves, i, 53; determinants, i, 63, 64, 66; quaternions, i, 126, 
127, 586; inverse elliptic functions, i, 132, 136, 152, 156, 162, 180; rotation of solid body, i, 
238, iv, 575, 576—7, 579; involution, I, 259, 263; definite integral, I, 270—1 ; dynamical differential 
equations, I, 276—9; elliptic functions, i, 290—300, 507, 587, xi, 452; demonstration of theorem 
on focal lines, i, 362—3; differential equations of Abelian functions, i, 366—9; skew determinants, 
i, 411; simultaneous linear transformations, I, 428; transformation of integrals, I, 440, 442; attraction 
of ellipsoids, i, 511—8; solution of equation x m —1 = 0, i, 564; Lagrange’s theorem, n, 7; geo 
metrical representation of elliptic integral, II, 56; in-and-circumscribed polygon, n, 141; partition 
of numbers, n, 248; lunar theory, hi, 13; canonical formulae for disturbed motion, hi, 76—7; 
problem of three or more bodies, m, 102; transformation, hi, 129; finite differences, m, 132—5; 
complete integral of partial differential equation, hi, 166; planetary theory, nr, 173; calculus of 
variations and differential equations, in, 174—84, 200, 202; De Motu Puncti singularis, in, 182—3, 
202; problem of three bodies, hi, 519—21, iv, 541, 548—51, 589, v, 23, vi, 183; Theoria Novi 
Multiplicatoris, hi, 183—5; theory of ideal coordinates, hi, 185; Encke’s memoir über die sped eilen 
Störungen, m, 179—80; in-and-circumscribed triangle, ill, 236; disturbed elliptic motion, hi, 
270—1 ; canonical system of formulae, hi, 290; reversion of series, iv, 30—7; transformation of 
elliptic integrals, iv, 60, 64; double tangents, iv, 187; conics, iv, 207; PfafPs problem, iv, 359— 
63; central forces problem, iv, 520, 589; Nova Methodus, iv, 515, 521, 589; elliptic motion, iv, 
522, 589; problem of two centres, iv, 530, 532, 589; motion of a single particle, iv, 537—8, 
589; motion in resisting medium, iv, 541, 589; motion of a point, iv, 547, 589; elimination of 
nodes, iv, 551, 589; transformation of coordinates, iv, 554, 557, 589; Weierstrass’s function al (x), 
v, 34—5; transformation of elliptic functions, v, 472, ix, 103, 113—75, xn, 59, 505—34; Canon 
Arithmeticus, vi, 83—6, xi, 85, 86; the Jacobian relation, vi, 467; geodesic lines on ellipsoid, vn, 
493; transformation of double integral, ix, 250—2, 254; epispheric integrals, ix, 321, 410—17; 
mathematical tables, ix, 472—3, 484—5; series, x, 25—7; Poisson’s theorem, x, 108—9, 110—3; 
theta functions, x, 156, 473, 478, 490, 496—7, xi, 41—6, xm, 559; roots of unity, xi, 58—60; 
Schwarzian derivative and polyhedral functions, xi, 149; hypergeometric series, xi, 178; Landen’s 
theorem, xi, 339; Abelian functions, xi, 454; theory of numbers, xi, 602; theorem in simultaneous 
equations, xn, 39; fraction theorem, xn, 123—5; Weierstrassian and Jacobian elliptic functions, 
xii, 425—7; sextic equation, xi, 389—401, xn, 493—9; sums of two series, xm, 50; modular 
equations, xm, 64; characteristic n and curves in space, xm, 469; sextic resolvent equations, 
xm, 473—9. 
Jacobian: defined, n, 319, iv, 607; of two quantics, n, 517; theory of, and polyzomal curves, 
vi, 566—8; the extended notion, vn, 134; of surfaces, vii, 134—6; of two curves, ix, 21; of 
quadric surfaces, x, 568; of six points, x, 613; rational transformation, xm, 116; (see also Quantics). 
Jefferson, T.: founder of Virginian mathematical professorship, xm, 43. 
Jeffery, H. M. : on quartic curves, xi, 408. 
Jellett, J. H.: theorem of, on attractions, i, 388—91. 
Jenkins, M.: Arbogast’s method of derivations, iv, 609 ; problem in factorials, vn, 597. 
Jerrard, G. B. : quintics, iv, 391—4, v, 50—4, 77, 89; theory of equations, xi, 520. 
Joachimsthal, F.: theory of covariants, n, 177, 234; theorem of, n, 521, xn, 594—5, 601, 629; normals 
of a conic, iv, 74—7 ; attraction of terminated straight line, vn, 33. 
Johnson, W. W.: matrices, xi, 252.