Reports on the Geology of the State of Maine. 145 



" The seaboard from Lubec to Thomaston was carefully examined, so 

 as to determine the nature and position of the different rocks. Then the 

 St. Croix was explored, and the line followed onward to Houlton. From 

 that place we proceeded to the St. John River, and pursuing its western 

 bank, we obtained a section of the strata, which cross the public lands, 

 and crop out along the course of that river. At the Grand Falls we took 

 canoes and examined the rocks and soils to the Madawaska River. By 

 following this plan, it will be seen on inspecting the map, that we have 

 made a reconnoissance of two sides of a very large square, forming the 

 eastern, and northern boundaries of the State." 



Dr. Jackson makes a division of his subject into topographical, 

 argicultural and economical geology ; the latter treating of those 

 substances which are of pecuniary value. The rocks enumer- 

 ated under the first head, are mostly members of the primary 

 class, forming the principal mountain elevations of the state, 

 and affording many valuable quarries of granite, and mica slate, 

 besides beds of white granular marble, and repositories of metal- 

 lic ores, which have already been made available to a consider- 

 able extent. To these he has added feldspar, suitable for por- 

 celain ware, granular quartz for the manufacture of flint glass, 

 foliated argillite or roofing slate, soapstone, serpentine, verd- 

 antique and pyritiferous slate, the latter employed in the making 

 of copperas and alum. The rocks of this class, as well as those 

 of later epochs, are frequently pierced through by powerful dykes 

 and veins of trap rock, which have left abundant proof, both 

 chemical and mechanical, of their firey origin, often changing 

 the rock into complete scorias, and forming, by their sudden 

 intrusions and interfusions, singular metamorphic combinations 

 out of the previously existing strata. The phenomena presented 

 by the beds of magnetic iron at Mount Desert and other places, 

 and also of the limestone at numerous quarries mentioned in the 

 reports, are of the most interesting character with regard to this 

 point. We doubt whether there are any where to be found re- 

 corded, facts more strongly attesting the igneous theory than are 

 presented in the reports, and as the author had become conversant 

 with analogous appearances while visiting many of the most 

 noted localities in Europe, his inferences will be received with 

 great confidence by the public. By a careful examination of the 

 trap dykes, he has shown that they were ejected by at least four 

 distinct paroxysms of elevation, the last dyke cutting through and 



Vol. XXXVI, No. 1.— Jan.-April, 183!). 19 



