b'TEVENSON, COAL BA8IN OF DEOAZEVILLE, FRANCE 383 



The essential features of the doctrine are that the basin was occupied 

 by a deep lake into which streams brought detritus of all kinds, mineral 

 and vegetable, to be deposited on the bottom in the order of their specific 

 gravity, very fine mineral matter being equivalent in distribution to plant 

 material. An important and attractive feature in Fayol's presentation 

 is the assertion that the coal deposit accumulating on the floor of a basin 

 may be, in its several benches, contemporaneous with deposits at several 

 horizons on the delta slope and thus, though resting on the floor, it may 

 be continuous with a bed which, at the shore, is 1000 feet above the bot- 

 tom of the basin. This is to explain the shoreward bifurcation of coal 

 beds. 



There is no room for difference of opinion respecting the origin and 

 mode of deposit of the inorganic materials in so far as they owe their pres- 

 ence to the transporting power of water; the only question is respecting 

 the origin and mode of deposit of the organic materials now found as coal 

 beds,^^ Unquestionably, the so-called delta theory explains satisfactorily 

 some features of the Decazeville as well as of other basins and, regarded 

 from this viewpoint, it has much to commend it. The flexibility and 

 adaptability of the doctrine in the hands of some of its adherents are 

 thought to be strong arguments in its favor ; but these matters are merely 

 , secondary. When a hypothesis is presented, the first question to be asked 

 respecting it is. Is it possible ? and the second is. Is it probable ? To be 

 convinced that this double test is essential at the outset, one need only 

 read some of the old works on cosmogony. Whiston is especially worthy 

 of study, for his work contains not merely a vast accimiulation of actual 

 facts, but also a wealth of mathematical demonstration which appar- 

 ently leaves nothing to be desired. No recorded observation, no known 

 fact, no phenomenon in earth, sea or sky failed as buttress to his elabo- 

 rate theory respecting the origin of things. That was the panacea for 

 perplexities in cosmogony, and its only defect was that it was based on 

 assumptions. Equally satisfactory as an illustration is the celebrated 

 hypothesis presented by Piazzi-Smyth respecting the great pyramid at 

 Ghizeh, which explained the purpose of every part of that structure so 

 beautifully as to arouse admiration as well as to carry conviction. The 

 only objection to it is that it is based on assumptions which are not true. 



" In passing, it may be well to mention a matter of minor importance. The writer 

 was Informed several times while in Decazeville that, as the mineral detritus is due 

 necessarily to transport, the natural conclusion would he that the interstratifled coal 

 had the same origin. Those who advance this argument seem to regard it as conclu- 

 sive ; but it Is not so. Applied to a coral reef inclosed in sandstone or to a sunken 

 swamp covered by sand on the New Jersey or Baltic shore, one would be iustifled in 

 asserting that since the reef and the swamp are of known in situ origin the inclosing 

 sand must also be of in situ origin. 



