Since the determinant having two identical rows, and an3 an3 ï¿½ï¿½ï¿½ ann vanishes identically; we have by development according to the elements of the first row a21Au+a22Al2 +a23A13+ï¿½ï¿½ï¿½ +a2nAin =0; and, in general, since a11A11+a12A12 +ai 3A13+ï¿½ï¿½ ï¿½ +ainAin = A, if we suppose the P h and k th rows identical a A +ak2 A 12 +ak3A13+ï¿½ï¿½ï¿½ +aknAin =0 (k > i) .and proceeding by columns instead of rows, a li A **lk** +a21A2k + a 31A3k+ï¿½ï¿½ï¿½+aniAnk = 0 (k .>

The Augustan age was one of those great eras in the world like the era succeeding the Persian War in Greece, the Elizabethan age in England, and the beginning of the 19th **Lk** y.

The formula, in the above case, is 3h{ *k(uo,o + 3 where u 0, 0 denotes the ordinate for which x=xo+Oh, y=yo+c¢k The result is the same as if we multiplied **lk**(vo 3v1+3v2 + v 3) by lh(uo 4u1 +u2), and then replaced uovo, uov1, ..

The above is a particular case of a general principle that the obtaining of an expression such as Ih(uo+4u1+u2) or **lk**(vo-1-3v 1 +3v 2 +v 3) is an operation performed on uo or vo, and that this operation is the suns of a number of operations such as that which obtains 3huo or 1kvo.

In any region of velocity where it is possible to represent p with sufficient accuracy by an empirical formula composed of a single power of v, say v m, the integration can be effected which replaces the summation in (to), (16), and (24); and from an analysis of the Krupp experiments Colonel Zabudski found the most appropriate index m in a region of velocity as given in the following table, and the corresponding value of gp, denoted by f (v)or v m **lk** or its equivalent Cr, where r is the retardation.

Now taking equation (72), and replacing tan B, as a variable final tangent of an angle, by tan i or dyldx, (75) tan 4) - dam= C sec n [I(U) - I(u)], and integrating with respect to x over the arc considered, (76) x tan 4, - y = C sec n (U) - f :I(u)dx] 0 But f (u)dx= f 1(u) du = C cos n f x I (u) u du g f() =C cos n [A(U) - A(u)] in Siacci's notation; so that the altitude-function A must be calculated by summation from the finite difference AA, where (78) AA = I (u) 9 = I (u) or else by an integration when it is legitimate to assume that f(v) =v m **lk** in an interval of velocity in which m may be supposed constant.

Whose co-ordinates are x, y, I, we draw PL normal to the plane yOz, and LH, **LK** perpendicular to Oy, 0