The aggregates of transition are harder and much more compact, than the secondary; they are also cemented by argil, taking a slaty form. This cement is in much greater quantity, in proportion to the particles cemented, and has the appearance as if the cement at the time of formation, had a consistence sufficient to prevent the particles from touching each other. They have, in common with all the transition rocks, a regular and uniform dip from the horizon, from 10 to 40 degrees; and sometimes more. This is perhaps the strongest mark of distinction which separates them from the secondary, which are horizontal, or follow the inequalities of the surface on which they were deposited. The transition are distinguished from the primitive in being aggregates of rounded particles, having little or no crystallization, and containing, or alternating with strata, which contain organic matter. The oldest red sandstone, with all its accompanying strata, I should incline to put into the transition, as having many of the properties of that class, and occupying the same relative situation in the stratification of the globe. It is at a constant dip (although small) from the horizon; the cement is in greater quantities in proportion to the particles cemented than in any of the secondary aggregates, &c. &c. The character of the secondary is a horizontal position, that perhaps does not admit of the same facility of examining the relative situation of its stratification. The compact limestone is, probably, with reason, considered as the lowest of the secondary formation, and always under the coal formation, but it appears to me that the secondary is deposited in basins alongside of one another, and that each basin has a different order of superposition, according to the nature of the agents employed in the deposition; that it is a partial, and by no means a general deposition. The secondary aggregates of sandstone and puddings have been evidently beds of sand or gravel, and of course, in that state would be called alluvial, but when cemented together by the infiltration of water, carrying along with it lime, iron, or any other body capable of agglutinating the particles together, become rocks, and may alternate in all proportions. I am therefore inclined to think, that in geology the best mode for the greatest part of the secondary would be to give the relative position of the strata of each valley or basin; and I am rather of opinion that they would all differ from one another. The French and English basin having chalk for the lowest stratum, which has occupied the geologists of both countries for these 10 or 15 years, is perhaps the best known; yet they do not know the relative position of the chalk and coals, because coals have not been found in the same basin with chalk: coals occupy basins filled with different kinds of rocks, and have no resemblance to the rocks found covering the chalk.