1 1 4 Notices respectifig Nelst Books. 



middle series I here estimate at 100 square miles; the upper 

 at 40 square miles. 



District IV. — Pembrokeshire contains only the lower se- 

 ries; it is much disturbed; and as we cannot consider every 

 bed extending throughout the whole area, I would on that 

 account deduct half the thickness of this series, and take it 

 here as only 17 feet. The area occupied I estimate at 100 

 square miles. 



From all this my general results are, for the lower series, 

 District I. 105 square miles; District II. 300 square miles; 

 District III. 120 square miles; total, 525 square miles, at 

 35 feet thick; and District IV. 100 square miles, at 17 feet. 

 For the middle beds. District I. 110 square miles ; District II. 

 ISO square miles; District III. 100 square miles; total, 360 

 square miles. For the upper beds. District I. 24 square miles ; 

 District III. 40 square miles ; total, 64 square miles. You 

 may easily calculate the tonnage hence resulting. You will 

 find in the Agricultural Survey of South Wales, vol. ii. p. 351, 

 a calculation, in which it is expressly said that deduction is 

 made for the less extent of the upper beds, which extent is there 

 assumed to be much more considerable than in my estimate. 



I have here, I think, fully set before you my principles and 

 method of proceeding, and you can readily judge for yourself 

 of their probable accuracy. In a letter to Dr. Buckland, I also 

 pointed out some directions in which I apprehended judicious 

 trials, by boring, might probably discover new coal-fields, after 

 our present ones are exhausted. For instance, I have little 

 doubt that such exist south of the Mendip Hills, towards the 

 Quantocks : for, since we know, from the dip of the Mendips 

 and from the quarries of Cannington Park, that there is in this 

 direction a limestone basin covered up by red marl which hides 

 its contents, those contents are, very probably, on the south 

 of the Mendip chain (as we know them to be in the basin to 

 the north of it) coal and coal-measures. Truly yours, 



W. D. CoNYBEARE. 



XVII. Notices respecting Ne'w Books. 



Description of the Petrifactions in the Museum of the University of 

 Bonn, bij Professor Goldfuss. 



THE Third Part of this valuable work has just appeared; and in 

 point of interest from its contents, and in the beauty of execution, 

 it is fully equal to the First and Second Parts. Although several copies 

 come to England, the work is not so generally known as it deserves; 

 for it is eminently calculated to advance geological science. Its title 

 is " Petrefacta Musei Bonnensis, — Abbildungen und Beschrei- 



bungen 



