relief, the moulds of the same being seen in the layer below." After mentioning that a continued shower of rain obliterates the more regular impressions, and produces merely a blistered or uneven surface, and describing minutely the characteristics of true rain marks in their most perfect state, Sir Charles adds:-- "On some of the specimens the winding tubular tracks of worms are seen, which have been bored just beneath the surface. Sometimes the worms have dived beneath the surface, and then re-appeared. Occasionally the same mud is traversed by the footprints of birds (_Tringa minuta_), and of musk-rats, minks, dogs, sheep and cats. The leaves also of the elm, maple and oak trees have been scattered by the winds over the soft mud, and having been buried under the deposits of succeeding tides, are found on dividing the layers. When the leaves themselves are removed, very faithful impressions, not only of their outline, but of their minutest veins, are left imprinted on the clay." This is a minor illustration of that application of recent causes to explain ancient effects of which the great English geologist was the apostle and advocate, and which he so admirably practised in his own work. It is also an illustration of the fact that things the most perishable and evanescent may, when buried in the crust of the earth, become its most durable monuments. Footprints in the sand of the tidal shore are in the ordinary course of events certain to be obliterated by the next tide; but when carefully filled up by gently deposited new material, and hardened into stone, there is no limit to their duration. Let us inquire how this may take place, and the tidal flats of the Bay of Fundy and Basin of Minas may supply us with the information desired. In the upper parts of the Bay of Fundy and its estuaries the rise and fall of tide, as is well known, are excessive. I quote the following description of the appearance they present from a work of earlier date:--