J. Starkie Gardner — Underground Heat. 397 



These ma}'- be the loosened and shifted abdomens of young in- 

 dividuals of C. stijgia or C. papilio, both common at Lesmahago. 

 They cannot be mistaken for the Carboniferous Acanthocaris, Peach, 

 or the Devonian Campecaris, Page. 



EXPLANATION OF PLATE X. 

 Fig. 1. Ceratincaris papilio, Salter. Entire specimen from the Upper Ludlow Shales, 

 Logan Water, Lesmahago, Lanarkshire. The abdominal segments are 

 displaced and reversed (as is very frequently the case in specimens from 

 Logan Water) and protrude from the rostral end of the carapace. Part of 

 the carapace of another specimen is seen near the posterior border. 

 ,, 2a. Ceratiocaris stygia, Salter, from the same locality and formation. 

 ,, 2b. Portion of the carapace, near the postero-dorsal line, showing the delicate 

 raised wavy lines with which the entire sm-face is covered (enlarged three 

 times) . 

 ,, 2e. The rostrum of same enlarged four times, to show the concentric striae 

 covering the surface. 

 Figs. I and 2a drawn of the natural size from specimens in the British Museum, 

 (Natural History) . 



{To he continued.) 



II. — Can Undergeound Heat be Utilized? 

 By J. Starkie Gardner, F.G.S. 



GEOLOGY has long been the handmaid of Engineering. Instances 

 are numerous in which the practical bearing of facts discovered 

 by the devotee of the one have been recognized and utilized by the 

 other. On the other hand, engineering enterprise has often put 

 geologists in possession of facts of the greatest value as bases for 

 fresh inductions. The subject now brought forward may perhaps 

 sooner, or in a remote future, furnish another instance in which 

 knowledge gained by the geologist may become available for a 

 great economic jDurpose. 



The subject of " Underground Heat " is one about which very little 

 is known even by the specialist. There is much divergence of 

 opinion as to the^form and conditions under which this heat exists, 

 and still more as to the depth at which it occurs. Whether the 

 interior of the earth is solid or fluid, hot or cold, is still a debated 

 subject ; though all leading geologists are at all events agreed that 

 it is hot, and many believe that it is partially fluid, the fluid being 

 situated beneath the solid crust, and resting upon a solid interior. 

 The question we have to consider is whether zones of considerable 

 heat are likely to be within a depth at which it might be practicable 

 to reach them. 



The paramount importance of the subject, and its pressing nature, 

 will come to be recognized when the scarcity of coal in this country 

 shall render it impossible for us to pay for the vast supplies of food 

 we are compelled to import from abroad either by it or by articles 

 produced by its aid. Our statesmen and others whom it may concern 

 will then perhajDS awake to the necessity of promoting experimental 

 research, and of obtaining new scientific knowledge; but let us hope 

 not too late to arrest a serious diminution of our national wealth. 



Coal began to be used as fuel in some localities about the 13th 

 century ; but until the beginning of the 17th, prejudice and other 

 causes prevented its coming into anything like general use. We may 



