SILURIAN EOCKS IX rrKIlTFOEDSHIRE. 245 



inches in diameter, and sometimes some feet in length, were being 

 brought up. The diamonds, as we then saw, are set in rows 

 tangentially at the bottom of a ring called the " crown," which, 

 being made to revolve while pressed down from above, cuts a circle 

 out of the rock in which it is working, leaving within the circle 

 cut away a solid column or " core " of the rock. This core, when of 

 a certain length, varying according to the diameter of the crown 

 used, and the hardness of the rock, is brought up entire. It there- 

 fore gives a perfectly true section of the stratum from which it is 

 taken, and allows of the angle of bedding or "dip," but not its 

 direction, being accurately determined, and of the fossils in the 

 rock-masses brought up being obtained and identified as readily as 

 if they were taken from an open section. In a letter which 

 appeared in the ' Times' about three weeks ago (19th May, 1879), 

 Mr. Eobert Etheridge, F.R.S. (whom we have this evening elected 

 an honorary member of our Society), made known the most im- 

 portant discovery in this boring of rocks of the age of the Wenlock 

 Shale. This letter has also appeared in the ' Geological Magazine,' *' 

 and in our county newspapers. 



Since this discovery was thus made known I have paid another 

 visit to the boring, and by the courtesy of Mr. Wild, the Eesident 

 Engineer, I am enabled to give a general section, which is as 

 follows :— Gravel, 14 feet; Chalk, 416 feet; Chalk Marl, 128 

 feet; Upper Greensand, 77 feet; Gault, 160 feet; giving a total 

 depth to the base of the Gault of 795 feet.f At this point I am 

 informed by Mr. Etheridge that there is a trace of the "Car Stone" 

 of the Lower Greensand formation. At the time of my visit — 

 the week before last — 43 feet of the "Wenlock Shale, with thin 

 intercalated bands of limestone, had been passed through, this 

 formation, as announced by Mr. Etheridge, having been found 

 to underlie the Gault. The dip of the Cretaceous rocks is very 

 slight (scarcely perceptible) ; that of the underlying Silurian rocks 

 is on the contrary very great, being 40 degrees. A few pieces of 

 shale I brought away show a sufficient number of fossils to prove 

 that the deposit in which they occur is of Wenlock age. J The 

 species are as follows : — Periechocrinus, sp. (a Crinoid) ; Atrypa 

 reticularis, ■MeristeUa tumida, Rhynchonella, sp., StropJiomena 

 depressa, 8. EuglypJia, and 8. rhomhoidaUs (Brachiopoda) ; 

 Orthonota rigida, and Pterincea, sp. (Conchifera). Mr. Etheridge 

 bus also kindly lent me a few specimens for exhibition, in- 

 cluding a Protozoon, Ischadites Koenigi, and a Trilobite, Phacops 

 caudatus. 



* Decade ii, vol. vi, p. 286.— 1879. 



t Too great a thickness seems to be assigned to the Chalk Marl and the Upper 

 Greensand; but the passage from the Lower Chalk, through the Chalk Marl 

 into the Upper Greensand, is here so gradual, that it is ditiicult to determine, 

 from the cores brought up in boring, the precise points where the lines of division 

 should be di-awn. It is owing to the absence of information due to this cause 

 that in some of the sections given in the plate illustrating this paper the Chalk 

 is not divided into the Upper and Lower Chalk and Chalk Marl. 



X The specimens were exhibited in the room. 



