Zoology and Botany, 853 



In South Wales the planes of splitting were in one direction with 

 very few exceptions. — Mr Phillips expressed his high satisfaction 

 at the result of Mr Hopkins' paper, and expressed a hope that the 

 phenomena of geology might, to a certain extent, be explained by 

 such simple laws as regulate the other branches of physical science. 

 With regard to the structure of rocks, which promised to throw so 

 much light upon the subject, he proposed a new term for it, the 

 symmetrical structure. In the examination of rocks under the throu 

 classes of Calcareous, Arenaceous, and Argillaceous, he had re- 

 marked, that the regularity of the structure increased with the an- 

 tiquity of the rock, which was well exemplified in the older slates and 

 limestones. For this there must be a cause, and this must be a cen- 

 tral heat, which has acted most upon the older formations, and least 

 upon the new. Illustrations of the eflFects of heat upon strata may 

 be obtained from those in contact with dykes, which produce sym- 

 metrical structure in rocks or clays through which they pass. In- 

 ternal heat must then have caused the regular structure so gene- 

 rally observed in rocks. The direction of the fissures pointed out 

 by Mr Hopkins in Derbyshire, corresponded with the observations 

 of Mr De la Beche in Cornwall, and of Mr Conybeare in Glamor- 

 ganshire. The phenomena of the direction of the joints were well 

 worth investigation, as there was much imcertainty involved. T^hey 

 evidently pointed out the weaker points, or places of least resistance, 

 where the disturbing force would operate with most efi'ect ; and 

 they may have been the result of consolidation, as we find them in 

 conglomerates, as well as in homogeneous rocks ; still it might be a 

 question, if they were formed before or after dislocation. 



Section D. — Zoologf and Botanv. 



Col. Sykes made a communication to the Section ** On the Cul- 

 tivated and Wild Fruits of the Deccan." 



Mr Mackay read the Report which he had been last year request- 

 ed to prepare, " On the Geographical Distribution of the Plants of 

 Ireland." This contained a catalogue of 195 of the more remarkable 

 species, with a comparative view of such as were common to the 

 neighbourhoods of Dublin, Edinburgh, and the south coast of Scot- 

 land. And Mr Mackay then entered into some details illustrative 

 of the more remarkable points of difference in the vegetation of 

 Ireland and Scotland. This difference might be partly ascribed to 

 the more southerly situation of Ireland, and the height of its moun- 

 tains being inferior to those of Scotland. Its greater exposure to 



