322 The AinericUll Gi'oIiHJ/.st. November, 189C 
giuD, wliich runs or exteuds itself iu acircular arch toward the northeast, 
are turned to the massive of Guayana, whose rounded domes of granitic 
rocks rise from the Tertiary plains, as islands out of the ocean, as far as 
is known. On the contrary, the Tertiary strata, wherever they have 
been elevated in massives, either cover the slopes of the mountain 
chains or form valleys {"vdHec de fracture") as the valleys of the Magda- 
lena and Canea rivers, and the section of the strata looks to the valley. 
The massive of Guayana appears to be the centre of the tlifferent 
mountains or Cordilleras belonging to Columbia, and upon which de- 
pends the direction of all of them. They rise to the west, in Columbia, 
and to the north in Venezuela, as the borders of a large circular crevasse, 
formed in the crust of the earth in the circumference of this primitive 
centre of elevation; crevasse which then was not recognizable l)y im- 
portant mas.sives in its total extension, but which marked the direction 
of the contemporaneous and future eruptions. 
The elevating force wliich caused the formation of the crevasse 
around the granitic centre, appears to have worked from east to west, in 
the primitive times, and plutonic epoch; that is it began to the northeast, 
reached its highest development in the north, and diminished more and 
more to the south. On the contrary, the last elevation of importance, 
which took place during the Tertiary volcanic epoch, followed an oppo- 
site direction . 
In the north the plutonic chains bordering the ocean reached their 
actual hight almost at the first elevation: at the end of the Cretaceous 
and Tertiary, they were only re-elevated; while in the south, they stood 
in part under the water, and only reached their actual form and hight at 
the end of tlie Tertiary, ])y the eruption of ti'achytic masses and lavas, 
which were very violent there, but became milder and milder toward the 
north. 
Report on the geology of northeastern Alabama, an<l adjacent portioiu of 
Georgia and Tennessee. C. Willard Hayes. Bulletin No. 4, of the 
Geological Survey of Alabama. 8vo. pp. 86, Montgomery. 1893 One 
plate of topographic outlines, and one geological map. 
This is a plain statement of the geological structure as made out in the 
field, over a critical area in the Appalachians, and covers all the Pale- 
ozoic from the Archii'aa to and including the lower Carboniferous, and 
some portion of the Coal Measures. The field work was done 1)y Mr. 
Hayes as an assistant on the V . S. Geological survey, and was reported 
to the state survey in pursuance of a compact between the two surveys 
in a cooperative plan for the examination of a section embracing the 
lower end of Lookout mountain, near Gadsden. The report, however, 
and the accompanying report, embrace considerably more area, that 
mapped l)eing al)Out 87 miles east and west, and 72 miles north and 
south. 
Mr. Hayes describes the remarkable fact, illustrated by the Kome 
thrust fault, that the lower rocks may be, and have been, faulted anil 
raised and thrust bodily over strata of much later date in that portion of 
