232 Geological and Miner alogicalJVotices. 



we have a. 68°, b. 112° = 180O; c. 108°, f/. .72°=180° ; from 

 which was constructed the annexed figure. These measurements 



Rhoviboidal Limestone. 



7 feet long, 5 wide, 1 thick. 

 were repealed on the same stone, and on different stones, and the 

 angles opposite to them were also measured, and found to vary in no 

 important manner, indicating a very remarkable regularity and paral- 

 lelism of the opposite sides. Running across the stones in two di- 

 rections, parallel to the sides, were distinct superficial cracks, and 

 cleavage through them would cut the mass into many precisely simi- 

 lar solids ; showing clearly, that the same cause that produced the 

 main fissures, now by the running water, enlarged to inches in width, 

 completely impressed its force and conferred a similar structure upon 

 the whole. The dimensions of these rocks are very various, as may 

 be seen by the measurement of some — ft. 1x1x6. 5x7x1 — 

 figured above, 4X6x24. This last, with the specific gravity of 

 2.5, must weigh 37 J tons. 



The attention now paid to the structure of rocks by such observers 

 as Conybeare, Sedgwick, De la Beche, and others, assures us of the 

 importance of treasuring up every fact, and in its description de- 

 scending to minute particulars, how litde soever we may at present 

 be able to appreciate them. I regret therefore that ray time having 

 been mostly devoted to the collection of minerals on that day, pre- 

 vented definite observations on some collateral points of importance, 

 as the dip, direction, Stc. of the strata — though my impression is 

 they varied litde from a horizontal position. 



This subject has excited new interest, and received new light from 

 Mr. Hopkins' researches, reported to the late meeting of the British 

 Association, and the facts constantly multiplying seem already to 

 promise the induction of some important general law. The remark 

 of Mr. Phillips that " the regularity of the structure (in the arena- 

 ceous, argillaceous, and calcareous rocks) increased with the anti- 



