A series £ a n is said to be summable (C, -1) to s if it converges to 5 and na n = o(l) [8]. It is well known that this definition is equivalent to t n^s (n->oo), where t n -s n +na n , s n = <*o + ••• + a n-The series is summable | C, -1 | to s if the sequence t = {t n } is of bounded variation (t e B.V.), i.e. £ | At n | = £ | ?"-/"_! | < oo, and £Af n = lim t n = j . t An equivalent condition is £ | a n | < oo, £a,, = s and £ | A(wa n ) | < oo. For, suppose that Yfin -s | C, -11. Since {^n} is the sequence of (C, l)-means of {;"} and since | C, 0 | c | C, 1 |, we have £ | a n | < oo and Yfln = s > whence £ I A(«a n ) | < oo. Conversely, £ | a n | < oo, Yfln = s a n d S I ^( wfl n) I < °o imply t e B.V. and £Af n = j+lim «a n . But lim na n = 0, since Z I On I < 00-Now let Yfln be a given series, with s n = a o + ... +a n , and define the sequence {t n } so that s. is the discontinuous Riesz mean of order 1 of t.:where 0 ^ X o < X y < ... < X n -* oo. Then we have = -n -.We shall say that £)*" = i(C, X n , -1) if and only if t n -+ 5 (n -»oo). By the regularity of (£, A n , 1) summability it is easily seen that an equivalent definition is that £a n converges to s and Hn a n = °(1)-If ^n = «»(C, ^«> ~ 1) reduces to (C, -1 ) , so that the new method generalizes the Cesaro method of order -1. We have used the notation (C, k n , -1) rather than (R, A n , -1) since a definition? of discontinuous (R, X n , -1) summability is already available. Now it is known [5], that (C, k) and (R, n, k) are equivalent for -1 < k < 2, and Dr Kuttner has shown me a proof, similar to that of [5], that (R, n, -1) implies (C, -1 ) but that the converse implication is false. Thus (C, X n , -1 ) is not equivalent to (R, X n , -1 ) even when X n = n.Using (1) we define £a n = 5 | C, X n , -1 | if and only if / e B.V. and t n -> s. Thus we have the inclusion | C, X n , -11 c (C, X n , -1 ) . We now give an equivalent condition for | C, X n , -1 | summability. THEOREM 1. Y. a n = s\C,X n ,-l\ if and only ifZ \ a n \ < oo, £a B = J a«^Z | AOyO | < oo.t All summations run from 0 to oo, and we take /_ i =0.