Correspondencer^Mr.John Toiing — Rev. Dr. Irving. 279 



cone Structure," mentioned in March Number of Geol. Mag., offered 

 a short explanation, that seems satisfactory to myself, and others, 

 that have seen my specimens, — regarding the radiated and inverted 

 structure of the cones, sometimes seen in nodular masses ; this 

 radiation, as stated in paper, pp. 26, 27, being due to secondary 

 causes that had acted on the cone stratum after the cone structure 

 itself had been developed. 



J point out in ray paper, in the first place, that the cones, in any 

 continuous level stratum, were evidently formed, through the upward 

 escape of gases from below, whilst the stratum itself was being 

 deposited the cones, invariably having their apices directed down- 

 wards to the lower part of the bed. In those cone strata where 

 there has been an after-tendency in the sediments to aggregate into 

 nodular masses, these nodules, in their contraction from lai'ger into 

 smaller dimensions, during their solidification, often show clear 

 evidence of the gradual pulling of the cones, from their former erect 

 position, all over the surface of the nodules ; they radiating, out- 

 wards, from the centre to the circumference, there also being 

 evidence of much crushing and distortion of the cone structure all 

 along their outer edges. I further point out that " where the con- 

 traction would be greatest, as in the more argillaceous nodules, 

 there may have been a bending, and in some instances a complete 

 inversion of the cones around the edges of the nodules." 



Since my paper was printed, in 1886, I have obtained many 



other illustrative specimens from our Scottish coal-field. These 



clearly show that the radiation and inversion of the cones, in 



nodular masses, was due to after secondary causes, the cone structure 



being first, the formation of the nodules being second, and the 



amount of radiation, and inversion of the cones, affords a measure 



of evidence as to the amount of contraction that has taken place 



amongst these nodules previous to complete solidification. 



HuNTEKiAN Museum, University, Glasgow. j yoUNG. 



May 2t/i, 1892. 



DISSIPATION OF ENERGY AS A GEOLOGICAL FACTOR. 



Sir, — Many readers of the Geological Magazine will, perhaps, 

 be glad to have their attention drawn to to the following passage, 

 which concludes an article by Lord Kelvin (P.E.S.), on " Dissipation 

 of Energy," in the "Fortnightly Review" for March, 1892 : — 



" The whole store of energy now in the sun, whether of actual 

 heat, corresponding to the sun's high temperature, or of potential 

 energy (as of a not run-down weight of clockwork) — potential 

 energy of gravitation depending on the extent of future shrinkage 

 which the sun is destined to experience, is essentially finite; and 

 there is much less of it now than there was three hundred thousand 

 years ago. Similar considerations of action on a vastly smaller 

 scale are, of course, applicable to terrestrial plutonic energy, and 

 thoroughly dispose of the terrestrial 'perpetual motion,'' by which 

 Lyell and other followers of Hutton, on as sound principles as those 

 of the humblest mechanical perpetual-motionist, tried to find that 



