The behaviour of tin under varying circumstances has frequently attracted the attention of chemists, and several authors have concluded that it is capable of assuming at least two different crystallographic forms, only one of which, however, has been thoroughly investigated. Since Miller described the beautiful pyramidal crystals of tin obtained by galvanic deposition from a solution of its protochloride, the anomalous appearance of those obtained in the dry way has often been remarked upon. Brooke obtained octagonal needles on slowly cooling molten tin and pouring off the fluid part. Pajot in a similar manner obtained rhombic prisms. Stolba obtained quadratic plates, whilst Breithaupt saw tin crystals, from Cornish smelting furnaces, which had the form of short hexagonal prisms (Miller considered them to be Cu Sn2). Lastly Rammelsberg inferred from the varying specific gravity that a not yet determined dimorphic form existed.