Page:Popular Science Monthly Volume 70.djvu/565

Rh the deposit consists of large beach pebbles mixed with coarse sand. So far as a buried marsh was concerned, the results were entirely of a negative character, but from the fact that there is a deposit of clay farther down, as well as from critical studies of the formation of marsh lands and of silted areas, prosecuted during the past summer, there seems to be great probability that one or both of such formations may lie beneath the beach at a horizon which could not be reached. In the absence of positive data, however, this source of gas must be

neglected, and the third alternative must be brought under consideration.

3. In making a section of the lower beach, as already recorded, it was observed that the superficial layer of sand, that which is directly acted upon by the water, consists of about one inch of freshly washed, fine sand with which are mingled numerous fragments of marine plants and even fragments of land plants, most of them in a fresh state but broken into small pieces by the recent action of the water and sand. Below this is a deposit of sand about six inches thick. This layer rests directly upon a mixture of beach pebbles and coarse sand extending to an unknown depth. It is the six-inch, or second, layer in which interest chiefly centers, since we find it to contain all sorts of organic debris, including marine algae, fragments of drift wood and bones of land animals. It in fact constitutes the general receptacle for all those organic remains which have been ground up in and transferred to it by the surface layer. It is clear that while this second layer may remain of approximately equal thickness, its organic content is