Prof. Williamson on a Cheirotherian Footprint. 155 



and stated that the only igneous rocks of the district, consisting of 

 a few dykes of felstone and greenstone, are of much later date than 

 the metamorphism, and have not altered the strata in contact with 

 them. These and other facts described in the paper had enabled 

 him to arrive at the following conclusions : — (1) That the strata 

 owe their metamorphism to hydrothermal action. (2) That the 

 varying 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. (3) That the 

 highly alkaline portions of the strata have been most susceptible 

 of change. (4) That in beds having the same composition, but 

 exhibiting various degrees of alteration, the intensity of the meta- 

 morphism has been in direct proportion to the amount of water 

 present in the strata. (5) That in some places the rocks have been 

 reduced to a pasty condition. 



3. " On a Cheirotherian Footprint from the base of the Keuper 

 Sandstone of Daresbury, Cheshire." By W. C. Williamson, Esq., 

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

 Owens College, Manchester. 



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

 in the Lower Keuper Sandstone at Daresbury 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 arrangement of the scales corresponds very closely with that 

 seen in the foot of the living Alligator ; many of them run across 

 the foot in oblique lines, as is common amongst living Crocodilians, 

 leaving no room to doubt that they represent true scales, and not 

 irregular tubercles, such as are seen on the skin of some Batrachians. 

 Traces of other impressions of feet occur on the slab, particularly an 

 imperfect one with much larger and more oblong scales, especially 

 under the heel ; and this difference is so very similar to what is seen 

 in the fore and hind feet of many Saurians, that Prof. Williamson 

 believed that they did not belong to a Batrachian animal at all, but 

 that they were Saurian, if not Crocodilian, in eve^ feature. 



4. " A description of some remarkable 'Heaves' or Throws in 

 Penhalls Mine." By J. W. Pike, Esq. 



This mine is situated in the parish of St. Agnes, in Cornwall, 

 and is, from the extraordinary dislocations and heaves of the lodes 

 and veins, without a parallel in any other part of the county. In 

 the immediate neighbourhood of the workings, taking the well- 

 known law that a lode or vein traversed is older than the one tra- 

 versing it, there are, in the order of formation, (1) four or five tin 

 lodes, (2) three or four " Downright" lodes, (3) innumerable 

 " gossans," (4) a great number of slides or faults, dipping at 

 various angles, (5) four cross courses, and (6) certain Caunting 

 slides. The mineral productiveness of the tin-lodes is increased by 

 the proximity of the gossans, but not by that of the slides ; and 

 although the dislocations are most perplexing to the miner, the district 

 has yielded great riches, and has been worked from time immemorial. 



