A SPECIAL exhibition to remain for three months has been arranged at the British Museum, Blooms-bury, at the head of the main staircase, to illustrate changes in flint, and the various methods of chipping it into implements. This supplements the permanent series in the Prehistoric Saloon (Case R), and is intended to make the grammar of the subject ar to those with restricted opportunities of f observing or collecting specimens. Patina has not yet been scientifically explained, but the examination of its varieties is a necessary step in solving the problem, and attention has been paid to the depths attained by patina on several specimens. Some old pieces have been re-chipped by living practitioners; and among those whose skill is exemplified may be mentioned Mr. J. Reid Moir, Mr. J. H. Sewell of Saskatoon, M. Coutier of Paris and Prof. A. S. Barnes. Some peculiar forms assumed by flints when fractured by man or natural forces are exhibited, and the technical terms used in prehistory are illustrated by typical specimens. Drawings of flaking methods presumably practised in the Stone Age are reproduced from Warren K. Moorehead's "Stone Age in North America", and a special feature is the wood-technique (blows delivered by a wooden baton) which is believed to have been adopted by St. Acheul man, the long narrow flake-scars due to this method helping to distinguish work of that date from the preceding Chelles or Abbeville culture.