676 KANSAS CITY REVIEW OF SCIENCE. 



The contraction of the limestone, however great, could not cause those fine 

 fractures so common in many places. Neither could it fracture the rocks at so 

 great a distance from the hmestone as has been done. I have often seen rocks 

 heated to a moderately high temperature and plunged into water. The sudden 

 cooling would cause them to crack in every direction, but their fractures would 

 be no more irregular or complicated than those of the chert rocks above alluded 

 to. The idea of their having been heated is entirely untenable, however : the 

 fossils in the limestones would contradict such views. They remain thus far 

 unexplained. 



THE FORMATION OF COAL. 



All attempts to explain satisfactorily the formation of coal have thus far 

 proved unsuccessful, though it is generally understood that it is the product of the 

 decomposition of vegetable matter. Just how that decomposition has been brought 

 about chemically is a matter which chemists have not as yet been able to solve. 

 The principal difficulty has been that it has been impossible to obtain a clear in- 

 sight into the chemical constitution of coal. It has been thought hitherto, and 

 this is still the popular belief, that coal is in the main pure carbon, mixed with 

 varying quantities of bituminous substances. It has been generally believed, that, 

 as the product of the distillation of coal is principally carbon, it would be safe to 

 conclude that free carbon actually does exist in coal. The fact that sugar, starchy 

 etc., under similar circumstances, leave a residuum consisting of carbon, has- 

 never been considered a proof that that element existed in these bodies in a free 

 state. It is well known that coals which may have the same percentage of carbon,, 

 hydrogen and oxygen do not by any means, in coking, yield the same products 

 of distillation, and we have a complete analogy for this in the behavior of cellu- 

 lose and starch when subjected to distillation. Evidence points to the conclusion 

 that coal is a mixture of many and complex compounds ; and the difficulty, 

 amounting to almost an impossibility, of separating these compounds, has much to^ 

 do in rendering a chemical solution of the questions involved in the formation of 

 coal a very arduous task. The production of coal by artificial means is met by 

 great obstacles, among which the absence of all knowledge concerning the condi- 

 tions under which that process actually took place is the principal one. The 

 question whether the vegetable matter to which our coal veins owe their origin 

 was amassed by drifting or was carbonized in situ, has been much debated, and 

 there has been much discussion on the point whether it was obtained from water 

 or from land plants. 



Dr. Muck, of Bochum, in a recent work, takes up the theory that algae have 

 mainly contributed to the formation of coal. It is urged that the remains of 

 marine plants are rarely found in coal veins, and that shells, etc., are not often 

 met with. Dr. Muck calls attention to the fact that marine plants decompose 

 easily and completely, losing their form entirely ; and that the disappearance of 



