It should be noted further that this is not a spelling list. If it is used as an aid in the construction Of spelling lists, the derived forms in s, ies, ly, er, r, est, st, 5, ed, d, ing, and n should be inserted. They may offer notable difficulty in spelling even when easily read and understood by derivation. A full account of the methods by which this list was selected, of the reliability of the credits attached to the words, and Of the uses to which the list may be put, will be found in an article of thirty-seven pages, entitled Word Knowledge in the Ele mentary School, by E. L. Thorndike, published in the teachers college record for September, For convenience in certain uses, there is added on pages 127 — 134 a list of the 2500 words of most wide and frequent occurrence, arranged in five sets of 500 each.