The decision of the Council to organize an excursion, the first since the Jubilee of the Society in 1926, arose from an invitation presented by Dr. A. E. J. Vickers, on behalf of Imperial Chemical Industries Ltd., to visit the anhydrite mine at Billingham. During the excursion the opportunity was also taken of visiting mineral localities in the northern Pennines (west Durham and Cumberland) under the leadership of Professor Wager and the writer. Accommodation was arranged in Durham at University College (by kind permission of the Master), and here, housed in the ancient castle, members enjoyed a comfortable stay. Transport each day was by private coach. The excursion was organized by Dr. G. F. Claringbull; the thanks of members are also due to Mr. E. Myers, secretary of the north-east section of the Society of Chemical Industry for his help in making local arrangements.

One of the problems which occupy the mineralogist as well as the geologist or pedologist is the mechanism of the formation and evolution of minerals in nature. In this general connexion we have been trying to clarify the possibility of passing from montmorillonite to chloritic minerals. Already in a previous work we showed that on precipitating magnesium with ammonia in the presence of montmorillonite, a substance is obtained which shows certain of the characteristics of vermiculite and chlorite. Having thus shown the possibility of passing from one type to the other, we wished to clarify the mechanism of the change. We wanted to know what are the conditions of the transformation, and then to follow the montmorillonite from the moment when it was in equilibrium with the solution of magnesium chloride to the end of the alteration. Finally, it had to be established to what extent the product obtained resembled or differed from the standard minerals. These different points will be considered in succession.