306 ANNUAL OF SCIENTIFIC DISCOVERY. 



slates, and form the cement at the points where we now find it. Dr. Hayes 

 also expressed, as his conclusions respecting the silification and consequent 

 preservation of organisms, that the process proceeded, step by step, with 

 the change of the organism into gaseous or aqueous matter. The mollusca 

 may be considered as simply organized water, for one hundred parts by 

 weight, often contain ninety-seven parts of water, vplatilc at 150 F. The 

 cell walls of albumino-gclatinous matter arc permeable, and the infiltration 

 of aqueous solutions of silicate of lime, would displace the water, gradually 

 depositing silica in a hydrous state, while the lime passed out with the water. 

 As consolidation is hastened by the decomposition of the animal matter, the 

 cell walls become changed, and the carbon or humus, in excess over that 

 which can become gaseous or aqueous, remains ; retaining as a mere skele- 

 ton the forms of the Avails. These silicificd forms are always porous, and 

 the flints contain the carbon of the organic matter, unevenly distributed. As 

 a beautiful illustration of silification, he referred to the specimens of trees 

 from California, frequently found in the explorations for gold ; many of the 

 specimens presenting the sap vessels entire in all their delicate organization 

 and nearly natural color, while near by, on the same piece, may be seen 

 black portions, in which the organized forms are lost, and the color is deep 

 black. This striking diversity is due to the fact that the wood at some 

 points had passed into the last stage of humus, carbon and water, before 

 silification took place, and hence the specimens present us with both silicificd 

 wood and silicificd charcoal. He observed the same changes, though less 

 obvious, while examining the highly interesting locality on the Island of 

 Antigua. 



Dr. C. T. Jackson remarked that he had examined the materials which 

 enter into composition and cementation of sand-stones and conglomerates, 

 and had found the cements to be different in different cases. In some, car- 

 bonate of lime forms the principal cement, in others, oxide of iron composed 

 a large proportion of the cementing matters, and in others, finer particles of 

 the same rocks that composed the conglomerate had formed a patse, which 

 had been hardened by the agency of heat and by the production of silicate of 

 lime derived, undoubtedly, from the decomposition of chloride of calcium. 

 He stated that when pebbles are moistened with a solution of chloride of cal- 

 cium, and then placed in contact and heated, the chlorine of the chloride of 

 calcium escapes, and the oxide of calcium or lime unites with the silex and 

 forms silicate of lime. There could be no doubt that the chloride of calcium 

 was derived from sea-water. Sometimes in the vicinity of trap dykes, as at 

 Purgatory, near Newport, Rhode Island, specular iron ore, evidently derived 

 from sublimation of oxide of iron from the chloride of iron, had invested the 

 pebbles with a thin crystalline film, which served as a cement. 



The cementing materials of some sandstones are so largely calcareous, 

 that on removal of the carbonate of lime by the action of acids, the stone 

 crumbles into sand. In such sandstones the carbonate of lime was probably 

 infiltrated as a bi-carbonate, and on losing one equivalent of carbonic acid, 

 the carbonate of lime would solidify in crystalline form and firmly unite the 

 sand, making it into a solid rock. 



