410 ON THE FORMATION OP THE CHALK STRATA, 



affords one of the most singularly beautiful phenomena that 

 I have had occasion to observe, connected with the mineral 

 kingdom. Some also appear to have been broken, before they 

 were inclosed in the flint, which has faithfully retained the im- 

 pression of the fracture as perfectly as the finest sealing- 

 wax. 



It is some years ago since I was first led to this observation. 

 While examining a flint which contained a portion of a be- 

 lemnite, I remarked on the calcareous radiated section of 

 the fossil two or three circular specks of flint ; and as they 

 also made their appearance at the other end, it occurred to 

 me to remove the calcareous matter by means of acid. On 

 the accomplishment of this, I was surprised and much inte- 

 rested to find, that these specks were the extremities of cylin- 

 drical portions of flint, having exactly the form and appear- 

 ance of arteries, and connected with each other, and with that 

 portion of the cone which remained, by means of smaller 

 fibres representing veins, and affording the most striking re- 

 semblance to an injected anatomical preparation. This disco- 

 very naturally raised my curiosity ; I searched my cabinet, 

 but in vain, to find specimens of the same kind. I endea- 

 voured, but with similar success, to procure some from 

 Ireland, and it was not till last autumn (1820,) when I was in 

 that country, in company with Lord Compton, that I was 

 enabled to procure the necessary supply. In the extensive 

 lime-quarries of Mr Farrel of Larne, I pointed out to the la- 

 bourers the belemnites imbedded in flint, which were quite 

 familiar to them, and for a trifling gratuity, an abundant quan- 

 tity was sent me in a day or two to Belfast. On submitting 

 them to the acid, almost all have afforded something ex- 

 tremely interesting and curious, and have opened up a source 

 of investigation which may probably lead to unexpected, re- 

 sults. 



The 



