To the Article Indication, Classes, Numbers, Validation, by A. N. White-head, Vol. XLIII, N.S., No. 171. Some misprints in the symbolrm of my article mast, I fear, make the whole unintelligible, apart from the following corrections. The proofs arrived from across the Atlantic on the day when I was overtaken by a dangerous illness which has incapacitated me for work during three months. Thus there has been no opportunity for autho-'s proof-corrections. I am obliged to the courtesy of the Editor (...) for the belated insertion of these corrigenda:— P. 286. Def. I, replace () by (3) P. 286. Def. II, replace 1st occurrence of p q by p g. P. 286. Def. III, replace Ec! x p by Ec x p. P. 286 Def. IV, replace p by p. P. 286 Four lines below, replace Ec! x Ec ! x by Eo x Ec! x P. 287. Lines 2 and 4, replace () by (). P. 287. Def. VIII, replace () by (). P. 287. Last line but one, replace o by 2, P. 291. Def. XXIII, replace (S) by (S). P. 292. Def. XXVII, end of 2nd line, replace xy by y. P. 292. Def. XXVIII, replace (c) by (c) P. 292. Def. XXVIII, replace c by c. P. 292. Def. XXIX, replace (1, 0) by , c). P. 292. Def. XXIX, replace (u + cm, v + c1) by (u + cm, v + c1). P. 293. Def. XXXI, replace (x) by (x). P. 293. Line 8, replace by . P. 293. Def. XXXIV, replace (x) by (x). P. 294. Lines 1 and 5, replace by Q. (shrink)