A. 8. Woodicard — A Microsaurian from the Coal. 211 



bulging up at the surface, is reduced by denudation to the form of 

 a mountain-chain. 



This theory has at different times received attention from geologists,' 

 and it has met with a considerable amount of adverse criticism. 

 Much of that criticism appears to me of a very forcible character, 

 but one of the strongest objections that can be brought against the 

 theory does not seem to have been generally noticed.' 



It is obvious that the heat which passes into and expands the 

 sediment must be withdrawn from the immediately adjoining parts 

 of the earth's crust, partly laterally, but chiefly from below; and 

 that the amount of heat gained by the sediment must be equal to 

 that lost by the crust. The increase in volume of the sediment 

 must therefore be accompanied by an equal decrease in volume of 

 that part of the crust from which the heat has been derived. Thus, 

 the sediment in expanding must follow a crust that is retreating, 

 and this retreat must take place, partly laterally, but chiefly down- 

 wards. Instead, then, of the sediment bulging up at the surface, 

 and ultimately forming a mountain-chain, its uppermost layer must 

 remain practically stationary (so far as the effect of the transference 

 of heat alone is concerned), while most, if not nearly all, of the 

 sediment below must subside. 



It may, in reply to this, be urged that the sediment will check 

 for a time the natural outward flow of heat from the earth's interior, 

 while the heat will continue to pass as before through the other 

 parts of its surface which are not areas of sedimentation. This may 

 be the case, but the amount of heat so checked cannot be great. 

 Supposing no heat at all to escape for some time through the 

 sediment, then its effect in raising the surface of the mass relatively 

 to that of the earth, can at the very most be represented by the 

 diminution of the earth's radius during that time; and this diminu- 

 tion will be small. The actual relative elevation of the surface of 

 the sediment, if there be any, will of course be very much less than 

 the change of radius. 



It follows, then, that the expansion theory is a theory of sub- 

 sidence, rather than a theory of elevation. 



VI. — On a Microsaurian (Htloxomus Wildi, sp. nov.) from the 



Lancashire Coal-field. 



By Arthur Smith Woodward, F.G.S., F.Z.S. 



DURING a recent examination of a collection of fossils made by 

 Mr. George Wild in the Burnley Coal-field, Mr. John Ward, 

 F.G.S., recognized a novelty in the small Microsaurian which forms 

 the subject of the following notes. The specimen was forwarded 



1 It has not, however, been overlooked by the Rev. 0. Fisher. " The heat 

 conducted into the new deposits," he remarks, "must be abstracted from the 

 couches beneath, so that there can be no absolute increase in the amount of heat 

 beneath the area in question except such as is supplied to it laterally, so that the 

 process must be excessively slow" (Physics of the Earth's Crust, second edition, 

 p. 132). I am indebted to my friend Mr. Fisher lor drawing my attention to this 

 paragraph, which, with the exception of the last few words, contains in a condensed 

 form the argument that follows. 



