534 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [JimO 6, 



the trap. Nor is there the slightest evidence of the existence of 

 any underlying mass of igneous rock, the heat of which might be 

 supposed by some to have caused the alteration of the strata. In the 

 second metamorphic area to which I have had occasion to refer, igneous 

 rocks are largely developed ; but, curiously enough, the most highly 

 altered strata occur at a distance from the intrusive traps. The 

 rocks immediately surrounding one large mass of felstone, about a 

 mile and a half in circumference, were for the most part quite 

 unaltered. They consist of conglomerates and chocolate-coloured 

 sandstones and grits. But outside of this unaltered area, felspathic 

 grits and sandstones have become felstones, and conglomerates 

 have been in places changed into bright-pink and fawn-coloured 

 porphyry. "We cannot, therefore, consider intrusive trap to have 

 been the source of heat in the metamorphic areas referred to, and 

 must thus accept the theory, so ably supported by many geologists, 

 that the temperature necessary to metamorphic action has been 

 derived from the central heat of the earth. 



The facts advanced in the foregoing communication seem to 

 prove : — 



1st. That the strata owe their metamorphism to hydrothermal 

 action. 



2nd. That the varjang mineralogical character of the rocks is 

 due principally to original differences of chemical composition, and 

 not to infiltration of foreign matter at the time of metamorphism. 



3rd. That the highly alkaline portions of the strata have been 

 most susceptible of change. 



4th. That in beds having the same composition, but exhibiting 

 various degrees of alteration, the intensity of the metamorphism has 

 been in direct proportion to the amount of water passing through 

 the strata. 



5th. That in some places the rocks have been reduced to a softened 

 or pasty condition. 



3. On a Cheirotheeiak Pootprint from the Base of the Ketjper 

 Sandstone o/Daresbury, Cheshire. By W. C. Williamson, Esq., 

 F.R.S., Professor of Natural History, Anatomy, and Physiology 

 in Owen's College, Manchester. 



[Communicated by the Assistant-Secretary.^ 



(The publication of this paper is unayoidably deferred.] 



[Abstract,] 



The specimen in question was discovered by Mr. J. "W. Kirkham, in 

 the Lower Keuper Sandstone at Daresbiiry Quarry. It differs from 

 all footprints hitherto obtained from this district, in being more 

 quadrate, and distinctly that of a scaly animal ; the separated toe is 

 also less recurved, and approaches nearer to the other toes. The 



