AMERICAN GEOLOGY MACLTJREAN ERA, 1785-1819. 



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and the various reprints of Maclure's. The classification adopted was 

 that of Werner, and hence, of course, purely lithological. The various 

 rocks enumerated and colored on the map were: I. The Primitive, 

 including granite, argillite, primitive trap, porphyry, and syenite; II. 

 Transition, including amygdaloid and graywacke; and III. Alluvial, 

 including sand, pebbles, clay, and peat. No granite was, however, 

 recorded as in place, the granite of Quincy and the areas west of north 

 of Marblehead being colored as syenite. The argillite was regarded 

 as the oldest rock occurring in the vicinity, and was represented as 

 forming gently undulating eminences in Charlestown, Watertown, 

 Chelsea, and Quincy. Greenstone, or primitive trap, was represented 

 as occupying all of the Marble head-Salem areas and large areas to the 

 west, including Stoneham and Lexington. Porphyry, "a compound 

 rock having a compact basis, in which are embedded crystals or grains 

 of other minerals of contemporaneous formation," and which passes 

 into both syenite and petrosilex, they found 

 in Maiden, Lynn, and Chelsea, while the 

 large area beginning at the shore east and 

 north of Lynn and extending southwest- 

 ward as far as Maiden, was colored as /» tro- 

 silex. A wide strip, extending from just 

 west of the Charles River to the coast, in- 

 cluding Brookline, Roxbury, and Dorches- 

 ter, was colored as graywacke, this being, of 

 course, the conglomerate of later writers. 

 On the northern and western edges of this 

 are narrow belts colored as amygdaloid, the 

 same being the rock later shown by Benton 

 to be melaphyr, or ancient basaltic lava flow. 

 The minerals as described were divided 

 into Class I. Earthy fossils; Class II. Saline fossils; Class III. 

 Inflammable substances; and Class IV. Metallick fossils. Under 

 Class I were included the phosphates and carbonates of lime, quartz, 

 such silicates as mica, shorl, feldspar, garnet, epidote, the amphi- 

 boles, etc., and such compound substances as petrosilex, basalt, 

 wacke, schaalstone, argillaceous slate, and clay. The second class. 

 Saline Fossils, included but a single species, sulphate of iron. Class 

 III included hydrogen gas and peat, and Class IV sulphides and 

 chlorides of copper, sulphide, oxide, and carbonate of iron, sulphide 

 of lead, and oxide of manganese. The classes were subdivided into 

 orders and the orders into genera, species, subspecies, and varieties. 

 Thus novaculite was considered a subspecies of argillaceous slate, a 

 species under Order II, Nonacidiferous substances of Class I, Earthy 

 fossils. Altogether some 21 species of Earthy fossils were recog- 

 nized, 1 of Saline fossils, 2 of Inflammable substances, and 8 of 

 Metallick fossils. These were all described in detail, their physical 



Fig. 2.— Samuel Luther Dana. 



