75 



HARDWICKE' S SCIENCE-GOSSIP. 



deposits or layers of shale of decidedly Permian age 

 and yielding a few characteristic remains generally 

 very much distorted. The upper seam of limestone 

 is a magnesian rock, yielding on analysis about 40 per 

 cent, of carbonate of magnesia and 55 per cent, of 

 lime. The lower limestone on the contrary is of 

 carboniferous origin and consists of thick blocks con- 

 taining at least 90 per cent, of carbonate of lime, 

 separated by thin layers of red shale. The general 

 dip of the strata -is to the N.E. at an angle of 10°. 

 The interest attached to this exposure arises in a great 

 measure from the mineralogkal nature of the rocks 

 which vary so much in colour and general appearance 

 from those previously described. Indeed, but for the 

 organic remains entombed we might almost imagine 

 that by some means or other we had wandered into 

 and were examining a Permian exposure in Durham, 

 though the subordinate mammillary or botryoidal 

 concretions so commonly and typically exhibited 



Fig. S2. — Map of Dumfries District, showing Limestone 

 exposures. 



there are entirely absent in the rocks under our 

 notice. The fossils, however, soon show the true 

 nature of the deposit and all doubt is quickly dissi- 

 pated by the presence of Productus giganteus and P. 

 semiretictilatus. These characteristic fossils are very 

 common and fairly perfect, but other species, 

 Zaphrentis, Euomphalus. Bellerophon, and Spirijcra 

 are rare, badly preserved, and their identification is 

 often a matter of considerable difficulty. 



Better exposures are found further north at New 

 Cumnock, near IMuirkirk, in which locality the car- 

 boniferous limestone is very extensively quarried. 

 The total depth of rock obtained here is 70 feet, while 

 the colour is again of the red tint imparted to it by 

 its proximity to magnesian strata. The fossil list is 

 a fairly long one and the diligent student should have 

 no difficulty in obtaining from the various quarries of 

 the immediate neighbourhood satisfactory specimens 

 of Orthis resupinata, Productus scmireticulatus, 

 Rhynchonella pugnus, Spirifera bisulcata, S. glabra, 

 BeUe7-opJiofi urii, Poteriocriniis crassus (parts), 

 Lithostrotio7i irregulare, Cyatliophylluin turhinatum, 

 Athyris roysii, A. ambigua. 



An excellent exposure occurs at Kellhead, a little to 

 the north-east of Annan where there is an outcrop 

 about 50 feet thick on the top of a hill or ridge over- 

 looking the Solway Firth. This place is certainly 

 worthy of a visit, not for the sake of its geological 

 interest alone, but also for the commanding view of 

 the surrounding district which can be obtained from 

 it. Nor is it possible to find a better or more typical 

 example of the true " Mountain Limestone " in respect 

 of its physical aspect, and a day spent in and about 

 this quarry and hill will do more to impress upon 

 the mind the distinctive features of the formation than 

 weeks of reading or class-room work. The red colour 

 still prevails, but the rock in many "parts is very friable, 

 owing to the fact that it is chiefly made up of Encri- 

 nites, held together by a binding of clayey-looking 

 lime. Want of space prevents us from describing at 

 length the various remains found at Kellhead, and 

 for the present we must only name those which occur 

 most abundantly and perfect in this very interesting 



Fig. 54. — Rhynchonella 

 pleurodon. 



F'g- 53- — Euomfhahts 

 pcntangulatus. 



quarry. Productus giganteus are again numerous, and 

 owing to the soft nature of the rock are not difficult 

 to extract. Euomphalus pentangulatiis appear very 

 perfect and in diameters varying from i| inches to 3 

 inches, while Bellerophon urii, and Nautilus dorsalis 

 are also frequently found indeed ; the writer remem- 

 bers seeing, nine years ago, a garden walk adjoining 

 one of the workmen's houses almost paved with 

 them. The siphuncled and chambered Cephalopod, 

 orthoceras is present in two or three species ranging 

 from ih inches to almost 5 feet in length. 



Compared with the Carboniferous Umestone of 

 England, we cannot help being struck with the many 

 points of contrast rather than of agreement which 

 present themselves to our notice. In the Carbonifer- 

 ous limestone of Scotland the beds and quarries are 

 by comparison poor in respect of depth or thickness, 

 and this is the chief reason why so many of them haye 

 been and are being abandoned. Wherever the beds 

 dip at an inconvenient angle, it is unremunerative to 

 follow them into the earth. And with regard to 

 organisms too, there is a remarkable paucity of species, 

 while even such as are to be found are generally far 

 behind their southern contemporaries in regard to 

 symmetry of form and state of preservation. 



