46 



Opal, Hyalite, Arragonite, Calcareous Spar, and a variety of Stil- 

 bite. The alkaline mineral waters acting on the components of the 

 bricks and cement formed double silicates most readily. The 

 Apophyllite was found in the cement and not in the bricks, while 

 Chabasie was found in the bricks. 



The conditions required for the formation of zeolite minerals 

 are fulfilled most perfectly, when trap rocks are thrown in a 

 molten state into beds of new red sandstone strata. The humid 

 sandstones and slates of that series are in the very condition 

 required for the chemical combinations to take place, under 

 the heat of the trap rocks, and the influence of heated saline 

 waters. 



k 



Trap breccia is a mixture of scoriaceous trap rock and sand- 

 stone. Amygdaloid is the scoria produced by the interfusion of 

 trap rocks and sandstone. Now in Nova Scotia, all along the 

 shores of the Bay of Fundy, we find in the utmost profusion the 

 Zeolites, Quartz and Amethyst geodes, Apophyllite, Stilbite, Mes- 

 otype, Analcime, Agates, &c., in the Amygdaloid, but not in the 

 compact trap rocks. 



So on the south shore of Lake Superior, where the trap rocks 

 have been erupted through and between the strata of new red 

 sandstone, we find the Amygdaloid at the point of contact of the 

 trap and the sandstone, and the Amygdaloid is filled with an 

 abundance of Zeolite minerals. Agates, Chalcedony, &c., while 

 the compact trap rocks are not charged with these minerals. 

 Dr. J. therefore inferred that these minerals were produced in 

 the Amygdaloid by agencies such as are cited by M. Daubree. 



Sea-water undoubtedly played a conspicuous part in effecting 

 changes in the composition of rocks, and in the formation of min- 

 erals contained in the metamorphosed rocks ; and it is probable, 

 in accordance with the views of Forchammer, Mitscherlich, Ma- 

 rignac, Senarmont, Favre, and Hunt, that the magnesia of the 

 Dolomites came from the decomposition of the chloride of mag- 

 nesium of sea-water, and that gypsum was also produced by the 

 reaction of the sulphate of soda on carbonate of lime. 



Forchammer found that when sea-water was heated with bicar- 

 bonate of lime, that magnesia was precipitated, and the proportion 

 augments at higher temperatures under pressure. He found also 

 that gypsum was decomposed in fourteen days when in contact 



