AMERICAN GEOLOGY MACLUREAN ERA, 1785-1819. 225 



words, no ""difficulty even in supposing it (i. e., the bridge) to have 

 proceeded from the hand of the Almighty as it is." 



Next to Maclure's Observations on the Geology of North America, 

 undoubtedly the most important of the early publications was Parker 

 Cleaveland's Elementary Treatise on Mineralogy and Geology, a work 

 of upward of six hundred pages, with live plates of 

 Treatfse'oii 8 crystal drawings and a colored geological map. 



G^iog a y?l8i a 6 nd Fo1 * most of the geological observations and for the 



map Cleaveland was indebted to Maclure and to writ- 

 ten communications from II. H. Ha} T den. The principal variation 

 from Maclure's map lay in the adoption of the suggestion of S. L. 

 Mitchill regarding the extension of the alluvial deposits on Long Island. 

 It further differed from that published b} T Maclure in 1817 in that a 

 large portion of southern and western Maine was colored as occupied 

 b} T transition rocks, this area having been left blank by Maclure. 



The classification adopted in the work was largely chemical, the 

 minerals being divided into (1) classes, (2) orders ? (3) genera, and (4) 

 species, his definition of species being "a collection of materials 

 which are composed of the same ingredients, combined in the same 

 proportions." 



In the tabular view given, all known minerals were grouped under 

 four classes, as follows: Class 1, substances not metallic, composed 

 entirely or in part of an acid; class 2, earthy compounds or stones; 

 class 3, combustibles, and class 1, ores. As was the case with all 

 writers of that day, basalt and several other compact rocks of indis- 

 tinct mineralogical nature were classed as minerals. Thus is found 

 under class 2, species 15, porceUanite; species 16, .silicon slate; species 

 32, i mi /■<//</, and species 34, basalt. This last was described as never 

 ciystallized but occurring "in large amorphous masses, but also under 

 a columnar, tabular, or globular form" and passing insensibly into 

 "greenstone, wacke, and perhaps clinkstone." 



Not only was the mineralogical nature of basalt little understood, 

 but even its relationship to volcanic rocks as well. It was described 

 as sometimes found in countries decidedly volcanic, but seldom near 

 the craters of still active volcanoes; " on the contrary, it appears at 

 the foot of volcanic mountains and sometimes almost surrounds them." 

 Some of the most noted localities mentioned are the Giant's Causeway, 

 island of Staffa, the Erzgebirge, Auvergne, etc. Its occurrence in 

 the United States was regarded as doubtful, though he noted its 

 reported occurrence on the Stony (Rocky) Mountains. It was regarded 

 as of both igneous and aqueous origin. 



Anthracite, which forms species t> under class 3, combustibles, was 

 described as "strongly resembling coal, from which, however, it 

 materially differs." It was said to occur in primitive or transitional 

 rocks, though sometimes connected with secondary rocks. Obviously, 



NAT MIS 1904 15 



