_Onu_.--I am not quite convinced by your arguments. Supposing the lands of New Holland were to be washed into the depths of the ocean, and to be raised according to the Huttonian view, as a secondary stratum, by subterraneous fire, they would contain the remains of both vegetables and animals entirely different from any found in the strata of the old continents; and may not those peculiar formations to which you have referred be, as it were, accidents of Nature belonging to peculiar parts of the globe? And you speak of a diluvian formation, which I conclude you would identify with that belonging to the catastrophe described in the sacred writings, in which no human remains are found. Now, you surely will not deny that man existed at the time of this catastrophe, and he consequently may have existed at the period of the other revolutions, which are supposed to be produced in the Huttonian views by subterraneous fire. _The Unknown_.--I have made use of the term "diluvian," because it has been adopted by geologists, but without meaning to identify the cause of the formations with the deluge described in the sacred writings. I apply the term merely to signify loose and water-worn strata not at all consolidated, and deposited by an inundation of water, and in these countries which they have covered man certainly did not exist. With respect to your argument derived from New Holland, it appears to me to be without weight. In a variety of climates, and in very distant parts of the globe, secondary strata of the same order are found, and they contain always the same kind of organic remains, which are entirely different from any of those now afforded by beings belonging to the existing order of things. The catastrophes which produced the secondary strata and diluvian depositions could not have been local and partial phenomena, but must have extended over the whole, or a great part of the surface, of the globe. The remains of similar shell-fishes are found in the limestones of the old and new continents; the teeth of the mammoth are not uncommon in various parts of Europe; entire skeletons have been found in America, and even the skin covered with hair and the entire body of one of these enormous extinct animals has been discovered in Siberia preserved in a mass of ice. In the oldest secondary strata there are no remains of such animals as now belong to the surface; and in the rocks which may be regarded as more recently deposited, these remains occur but rarely, and with abundance of extinct species. There seems, as it were, a gradual approach to the present system of things, and a succession of destructions and creations preparatory to the existence of man. It will be useless to push these arguments farther. You must allow that it is impossible to defend the proposition, that the present order of things is the ancient and constant order of Nature, only modified by existing laws,