III. 



ANCIENT SLATE-INSCRIPTIONS. 



" It is a lonely place, and at the side 

 Rises a mountain rock with rugged pride, 

 And in that rock are shapes of shells, and forms 

 Of creatures in old worlds." 



CEABBE. 



'0 student of Geology is likely to be very 

 long before he is introduced to the 

 Graptolites, and having once seen those 

 lustrous pyritous impressions which in 

 many localities cover the Silurian slates as though 

 with silvery hieroglyphics, he will never forget 

 them. They are as curious as they are beautiful, 

 and no extinct forms have given rise to more 

 discussion respecting their structure and palaeonto- 

 logical significance. 



The name of these fossils was given to them 

 from their resemblance to lines of writing, their 

 similarity to some of the old inscribed stone slabs 

 being very striking in the case of a not overcrowded 

 layer of slate. They have never been found outside 

 the Cambrian and Silurian systems, being most 

 abundant at the base of the Silurian formation, and 



