200 Coast Survey Report for 1853. 
We have then distinguished four classes of crystalline lime- 
stones: first, those of the Laurentian series with their accompa- 
nying garvetiferous gneiss, labradorite and hypersthene rocks; 
secondly, those of the Lower Silurian formation, with their at- 
tendaut auriferous rocks, talcose slates and chromiferous serpen- 
tines; thirdly, those of the Upper Silurian age, with their asso- 
ciated calcareo-micaceous schists; and fourthly, those which be- 
long to the gneissoid rocks of eastern Massachusetts, and are 
probably of the Devonian period. 
I have endeavored in this paper to bring together the facts 
known with regard to the different crystalline limestones, aud 
their associated strata in this portion of the continent, and to 
show how far these may serve as a guide in the geological inves- 
tigation of the metamorphic rocks. While the result confirins 
the observations of European Geologists, that similar crystallized 
minerals may occur in the metamorphic limestones of very difler- 
ent geological epochs; it also shows, that within certain limits, 
the mineral characters of the altered silicious strata, may serve a 
important guides to our investigations. 
“oe ee 

Art. XXV.—Documentary Publications and Science in the 
Coast Survey Report for 1853.* 
* Report of the Superintendent of the Coast Survey, showing the progress gies 
Survey during the year 1853. Washington, D.C. Robert Armstrong Public 64 
pes 1854, Quarto Report, 88 pp. Appendix, 180 pp. Total pages 276 and " 
