In justice to Professor Dana it should be stated that he included in this theory of formation all lunar craters, even those of small size and possessing central cones; and he put forth his views in opposition to the eruptive theory which we have set forth, and which was briefly given to the world more than twenty-five years ago. As regards the smallest craters with cones, we believe few geologists will refuse their compliance with the supposition that they were formed as our crater-bearing volcanoes were formed: and we have pointed out the logical impossibility of assigning any limit of size beyond which the eruptive action could not be said to hold good, so long as the central cone is present. But when we come to ring-mountains having no cones, and of such enormous size that we are compelled to hesitate in ascribing them to ejective action, we are obliged to face the possibility of some other causation. And, failing an explanation of our own that satisfied us, we have alluded to the few hypotheses proffered by others, and of these Professor Dana’s appears the most rational, since it is based upon a parallel found on the earth. In citing it, however, we do necessarily not endorse it. CHAPTER X. PEAKS AND MOUNTAIN RANGES. The lunar features next in order of conspicuity are the mountain ranges, peaks, and hill-chains, a class of eminences more in common with terrestrial formations than the craters and circular structures that have engaged our notice in the preceding chapters.