136 Prof. How on the Mineralogy of Nova Scotia. 





I. 



II. 



Water . 



15-81 



14-34 



Alumina . 



8-72 



5-89 



Lime . . 



. 13-60 



11-08 



Potassa . 



3-35 



4-71 



Silica . . 



58-47 



64-33 



99-95 100-35 



which show that while there is an approach to the composition 

 of stilbite, the other minerals are quite different in composition, 

 and have introduced a good deal of lime and potash. I con- 

 clude that the solid is chiefly made up of stilbite and apophyl- 

 lite with green earth. We have here, no doubt, an illustra- 

 tion of the action of water in filling cavities formed by the 

 passage of vapours in the original condition of the rock. In 

 a very interesting paper on Trap Rocks of the Connecticut 

 Valley (Silliman's Journal, March 1875), analogous effects are 

 described by Mr. G. W. Hawes, who says (p. 191), in refer- 

 ence to the chemical composition of the rocks and the contents 

 of cavities, " That there was such a passage of vapours through 

 the molten mass is evident ; for the rock of some dykes contains 

 long pipestem-like cavities which were made by the ascend- 

 ing vapours, and which are generally filled with calcite." I 

 may mention that the contents of cavities mentioned by Mr. 

 Hawes as occurring in the Connecticut-valley trap rocks, bear 

 a close resemblance to those I have observed in those of Nova 

 Scotia on the Bay of Fundy. In this circumstance we have 

 additional evidence as to the fundamental similarity shown by 

 Professor Dana to exist between " the eruptive rocks (or trap) 

 of the Triassico-Jurassic areas of the Atlantic border, from 

 Nova Scotia to the Carolines, all of which belong to one epoch, 

 and are solely varieties of dolerite — rocks made up essentially 

 of labradorite and pyroxene with more or less magnetic iron- 

 ore in disseminated grains or crystals " (Silliman's Journal, 

 August 1873, p. 105). With reference to the last-named con- 

 stituent, I offer the following remarks. 



Magnetite. — In various parts of the trap between Blorindon 

 and Brier Island veins and pockets of magnetic iron-ore exist. 

 The ore presents a general similarity of appearance : it is fre- 

 quently compact and massive, sometimes crystallized on the 

 surfaces when veins are only partially filled ; it is generally 

 associated with amethystine quartz-crystals (occasionally in 

 specimens of very deep colour) or other forms of silica. On 

 Digby Neck are several localities, at some of which the ore 

 occurs with red haematite ; altogether these deposits have fur- 

 nished a few hundred tons for smelting. I made analyses of 



