THAT certain ancient silver articles, including coins, have in the course of time become exceedingly brittle is fairly well known. Silver coins which have been struck must have been ductile at the time of manufacture and hence have become brittle as a result of some sort of ageing process. This form of embrittlement has been observed in silver coins of ancient Greece, of late Roman times, in Saxon and English coins, and in late medieval coins of India [i]. An interesting example of the last is provided by a very base coin, probably of Muhammad III (A.D. 1325-51), which fractured into three pieces while being sent by post from London to Manchester. This type of brittleness is, therefore, of the widest geographical and historical distribution. So far as the authors are aware, no detailed study of this most curious change has so far been made. One of us has been informed by Dr C. H. Desch that M. Babelon is disposed to attribute it to some effect resulting from corrosion, but it is obvious that this cannot be at any rate the whole story, since we have seen Saxon coins in mint condition which have become as brittle as glass. Further, this type of embrittlement cannot be analogous to that reported by Roberts-Austen [2] in gold, since the bars investigated by him were always brittle, whereas here some secular change must have taken place. Fifteen exceedingly brittle silver coins were subjected to microscopic examination. These included Greek coins, siliquae of Gratian and Theodosius I, an English penny of Henry III, a groat of Edward III, a groat of Mary, a halfgroat of Elizabeth, and a shilling of Charles I. An Irish groat of Henry VIII and a Scottish quarter merk ofJames VI were also examined. During preparation, the coins were held in a perspex clamp, electrolytically polished in Gilbertson and Fortners's or Hogaboom's reagent, and then etched either by shortcircuiting the electrode terminals for a few seconds, or more usually in 4% nitric acid in alcohol.