For some time past we have been drawing attention to some of the dicta of Geology, which appear to have a less solid foundation than they should have to authorize the positive manner in which they have been enunciated. Similar doubts on some points would appear not to be absent from other minds. Mr. Page has just issued a little work reviewing the state of the popular doctrines of our science, and Mr. Sterry Hunt has appropriated to the explanation of the higher Palaeozoic climate Dr. Tyndall's memorable researches on the relations of gases and vapours to radiant heat. Heat, from whatever source it may proceed, passes through hydrogen, oxygen, and nitrogen gases and dry air, with nearly the same facility as through a vacuum, and these gases are thus to radiant heat what rock-salt is amongst solids. Glass and some other substances which are readily permeable to light and to solar heat, offer, as is well known, great obstacles to the passage of radiant heat from non-luminous bodies, and many vapours and gases have a similar effect in intercepting the heat from such sources. Thus, for a vacuum the absorption of heat from a body at 212° Fahr. is represented by 0, that by dry air as 1, while the absorption by an atmosphere of carbonic acid gas is 90; by one of marsh-gas, 403; by olefiant gas, 970; and by ammonia, 1195.