IN a long communication sent to us by Mr. J. H. Goodchild, dealing with the distribution of sodium and calcium, reference is made to Prof. J. Joly's calculation of the age of the earth from the saltness of the sea, a calculation based on the assumption that the salt in the sea has been carried there by streams and rivers and has been derived by solution from the land. In opposition to this view Mr. Goodchild suggests that, contrary to the notions held at the present day by geologists, salts pass from the ocean to the. land, and are being fixed as new mineral combinations in the rocks through which they percolate. He regards sedimentary rocks, such as sandstone and shale, as unstable, and liable to admixture with one another as well as to modification by the action of soluble substances like salt and calcium carbonate. As examples of changes of this sort he points to the dolomitisation of limestone, the formation of haematite at and near the surface, concretions in the coal measures, and vein formations of quartz, calcite, fluorspar, and barytes.