212 



Bushin — Banded and Brecciated Concretions, 



walls, or tabular crystallizations, of agate, I shall name Mural agates ; 

 and they are connected, on the one hand, with Folded agates, by a 

 series in which tabular portions of the external matrix are torn off 

 like pieces of broken slate, lifted up into the agatescent mass, and then 

 encrusted with folds of chalcedony ; on the other hand, when the 

 Mural fragments become curved, they are connected with a great 

 jasperine group of the most curious interest, which I shall examine 

 under the general term of Involute Agates, consisting of bands of a 

 consistent structure, broken up (or fragmentarily secreted), Fig. 5, a, 

 in fine specimens disposed in curves resembling the contour of a 

 haliotis shell. Fig. 5, b, but in less developed examples forming broken 

 vermicular concretions in a jasperine paste, Fig. 5, c. It is almost 



Fig. 5. 



A. B. C. 



impossible without microscopic examination to distinguish some of 

 these shell-like concretions (of which the most delicate are white, 

 closely crowded, and surrounded by milky chalcedony), from true 

 organic remains ; and to my mind perhaps the most singular fact, of 

 all that are connected with minor physical phenomena, is this 

 apparent effort of the occult natural powers to deceive their investi- 

 gator, by making one thing resemble another. There seems to be a 

 mocking spirit in Nature which sometimes plays with its creatures, 

 as in the orchis tribe of plants, or the mantis group of insects ; and 

 sometimes deliberately connects two totally different systems of its 

 work by deceptive resemblances, causing prolonged difficulty or error 

 in the attempt to discriminate them. In this subject before us, for 

 instance, the inorganic secretions of chert and flint are connected, by 

 the most subtle resemblances, with those which have organic nuclei ; 

 the filiform and foliated secretions of chlorite, and the flamelike and 

 infinitely delicate mossy traceries of jasper, pass with the cunningest 

 treason into the organisms of altered sponge and wood ; the pisolitic 

 and radiated-crystalline agates confuse themselves with true corals ; 

 the involute agates with shells ; the rolled breccias with slowly 

 knotted secretions ; and all the phenomena of successive deposits, 

 quite inextricably with those of segregation ! I imagine, however, 

 that the reader must have had enough, for the present, of these mere 

 statements of doubt, and as my next subject, mural agate, is a very 

 difficult one, I shall delay the paper for some time ; but meanwhile, 

 if any good chemist would set briefly down for me what is now 

 positively known of the fluent and gelatinous states of silica, and 

 silicate of iron, with respect to their modes of separation, when 

 undisturbed, from other substances, it would be of the greatest 

 service to me (and not, I should imagine,) irrelevant to the general 



