My letter in the March Number of the Geological Magazine, asking for a description of the “Herschel-Babbage” theory of Mountain formation, appears to have called forth Mr. Davison's “Note on the Expansion Theory of Mountain Evolution,” in which he favours us with his definition of the “fundamental principle of the theory of terrestrial evolution which has sometimes been called the ‘expansion theory.’”

Glen Fruin is a quiet secluded glen, about six miles in length, extending in a north-westerly direction between Lochlomond and the Gareloch, and opening off the neck of land which divides those lochs at between 200 and 300 feet above the sea. To the south-east, it slopes towards Lochlomond, of which the Fruin water is one of the principal affluents. On the west it is divided from the Gareloch by a range of hills 1000 or 1200 feet in height, which at its upper extremity subside into a col or pass of 600 or 700 feet. This upper part of the glen is composed of the mica and clay slates common to the Western Highlands. The lower part is formed of beds of the Calciferous Sandstone series, which have here been faulted down against the older formations.

The high price of all heavy liquids, and the consequent care that has to be taken in using them, the latter of course entailing great expenditure of time, were the reasons which caused me to make experiments, with regard to the manufacture of Klein's solution (borotungstate of cadmium) on a small scale. The price quoted in a well-known chemical manufacturer's price-list is 3s. 6d. per oz. My experiments have shown me that it can be made for about 7d. per oz., plus the value of the time of the maker. The process is very simple, and not much time is necessary in making it. A rough outline of the method of preparation is given by Dr. Klein in the Comptes Rendus, vol. xciii. August, 1881.