352 



LIEUT.-GEN. C. A. MCMAHON OX 



[May 1900, 



following minerals is doubtless due : namely, graphite in lustrous 

 hexagonal tabular crystals, a pink mica, and magnetite. The two 

 former are abundant. 



These limestones also con- 

 tain a silvery mica, chlorite, 

 ferrite, pyrite, and quartz ; 

 all of which, with the possible 

 exception of the silvery mica, 

 appear to be due to subse- 

 quent aqueous action. Hot 

 springs are numerous in this 

 series. 



The limestones are very 

 pure. 1 They dissolve com- 

 pletely and readily, with brisk 

 effervescence in dilute hydro- 

 chloric acid, and some that I 

 analysed contained calcium 

 carbonate 96-08, magnesium 

 carbonate 1-93, and iron 1-99 

 per cent. When struck with 

 a hammer or rubbed together 

 the limestones smell of sul- 

 phuretted hydrogen, which 

 seems to indicate the original 

 presence of organic matter. 

 The gas generated from it is 

 still retained in the pores of 

 the rock. 



Capt. Roberts informs me 

 that the stinkstones in this 

 section occur in a series of 

 about twenty beds inter- 

 calated with mica-schists. 

 Each bed is from 20 to 30 

 feet thick, and is made up of 

 a central band of solid lime- 

 stone, with innumerable thin 

 beds of limestone, varying 

 from 1 to 12 inches in thick- 

 ness, on both sides of the 

 central band. 



The whole twenty beds, 

 with their intercalated mica- 

 schists have, Capt. Roberts 

 informs me, roughly speaking 

 a thickness of 2000 feet. The strike is east and west, and the dip 

 about 70° south. The stinkstones crop up again about 8 miles 



1 Some specimens are streaky-looking, from the segregation of the contained 

 minerals. 



