68 ON THE ORGANIC STRUCTURE OF FLINT AND OF MEERSCHAUM. 



aid of acetate of rosaniline, the pale green substance in the green 

 marble from Connemara may be shown to be a very beautiful 

 fossil sponge.* This is especially interesting, as, on account of 

 its being in age and appearance not unlike the Eozoonal Lime- 

 stone, the Connemara marble has been carefully searched, I believe 

 hitherto without result, for organic remains. Perhaps this method 

 may now lead to their detection, not only here, but also in other 

 places where their existence was not even suspected. 



In the same way I have found the soluble-silica rock from the 

 neighbourhood of Farnham, in Surrey, to be a silicified sponge. 



Those who wish to study the chemical action of silica on the 

 aniline bases will find some interesting matter in an article by 

 Wm. Skey, " Chem. News," vol. xxx., p. 45 ; also in one by M. 

 Eeimann, "Chem. News," vol. xxii., p. 83, and "Journ. Chem. 

 Soc," vol. xxiv., p. 452. 



The development of fossil structures to which I have alluded 

 appears to be due to the fact that one portion of the mass is in 

 such a condition that it is more readily acted on by the reagent 

 than the other. 



The acetate of rosaniline is by no means the only substance that 

 I have found useful in discovering these hidden structures ; nitrate 

 of silver is sometimes even more efficacious, and the acetate of iron 

 will often answer the purpose. The object to be effected is to 

 render one portion opaque or strongly coloured relatively to the 

 other, so that the difference between them may be detected, which, 

 while they are both of the same colour and equally transparent is 

 impossible. 



* Also that the serpentinous rock, largely quarried in the Isle of Anglesea, 

 about 50 years ago, and used in London for ornamental purposes under the 

 name of Mona marble, contains a considerable amount and a considerable 

 variety of similar structures. 



