292 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



Ardennes, which have lately been studied by Poussin and 

 Renard (Record for 1877, p. 1G9). In the belt of the Ar- 

 dennes in France and Belgium is found a series of argil- 

 lites and crystalline schists, including more coarsely crystal- 

 line masses of rock, with well- developed feldspar, quartz, 

 hornblende, epidote, etc. Some of these have been variously 

 regarded as detrital and as intrusive rocks, but are by the 

 writers just named shown to be indigenous masses. These 

 rocks, the Ardcnnian series of Dumont, and by him divided 

 into the subordinate Revinian, Devillian, and Salmian groups 

 (called by him systems), have been described by different 

 observers as altered Devonian or Silurian, and by the writ- 

 ers just named are conjectured to belong to the lower por- 

 tion of the Cambrian. As shown by Gosselet, they formed 

 islands in the Devonian sea, and in one part of the region, at 

 Haybes, include schists with Oldhamia and undescribed grap- 

 tolites, the relation of which to the crystalline schists is not 

 apparent. In the opinion of Hunt, who has lately examined 

 the region, the great mass of these rocks is probably pre- 

 Cambrian, and has in part resemblances w 7 ith the Huronian, 

 and in part with the argillites of the Taconian (Lower Ta- 

 conic, Emmons), which includes considerable developments 

 of crystalline schists. The purple argillites of Yiel Salm, in 

 the Ardennes, are remarkable for containing thin interstrati- 

 fied layers of a peculiar cream-colored rock, long esteemed as 

 a fine hone-stone, or coticulite. This has lately been exam- 

 ined by Renard, who finds these layers to be made up of mi- 

 croscopic grains and crystals of manganesian garnet, with oc- 

 casional tourmalines, and a green crystallized mineral, which 

 is believed to be either epidote or chrysoberyl; the whole im- 

 bedded in a hydrous micaceous mineral allied to damourite. 

 These crystalline minerals are also found in smaller quantities 

 diffused through the accompanying argillites. 



BRITISH SERPENTINES. 



Bonney has lately studied with much detail the serpen- 

 tines of Cornwall, with their associated hornblendic and chlo- 

 ritic schists, and adheres to the old view that the serpentines 

 themselves are eruptive masses. lie has since carried his ob- 

 servations to the coast of Ayrshire, where similar serpentine 

 rocks and crystalline schists are met with, and extends to 



