[Proceedings United States National Museum, 1881, — Appendix.] 



SMITHSONIAN INSTITUTION. 



TINITEID STATES N ACTION J^I^ Ml XJ S E XJ M! . 



No. 9. 



CIRClJIiARIlVREFEREIVCE TO THE BVlIiDINO-ISTOIVE COIil^ECTIOIV. 



The special investigation of the building-stone industry of the United 

 States made by the Tenth Census is now nearly completed, as far as 

 field work is concerned. It has been a part of the work of this investi- 

 gation to forward to the National Museum samples of all stones quarried 

 for purposes of construction. These specimens were mostly of such 

 size that they could be dressed into four-inch cubes. Over 3,000 such 

 specimens have been received at the National Museum, and nearly one- 

 half of the number have already been dressed in the following manner: 

 Polished in front; drafted and pointed on the left-hand side; drafted 

 rock face upon the right-hand side; entirely rough behind, and rubbed 

 or chiselled ui)on the top and bottom. As soon as dressed, the samples 

 are placed in suitable cases, where they may be examined by all who are 

 interested in building stones. 



All the building stones of the country are thus brought together for 

 study and comparison. Stones which have not been quarried until 

 recently may be comi^ared with stones of the same kind which have 

 long been in use, and the qualifications of which are well known. 



There is also quite a large collection of foreign stones with which 

 comparisons may be made. Nearly every foreign quarry, the product of 

 which is in the markets of this country, is represented by a specimen. 

 There are also quite a number of specimens from foreign quarries, the 

 products of which have been but little or not at all in the markets of 

 the United States. 



This collection is now perhaps the largest, most complete, and sys- 

 tematic of any of its kind in the world. 



Thin sections for microscopic examination are being prepared from 

 all the difierent specimens. The purposes of the investigation demand 

 a determination of the compositions and structures of the various rocks, 

 as these in combination with the location and geological features deter- 

 mine the applicability of the stones to various uses, and explain their 

 peculiar properties, and the desired results are most directly obtained 

 by the microscopic examination of thin sections. 



This method of study in the hands of the microscopic lithologists has 

 been most fruitful in developing valuable and interesting knowledge of 

 a scientific character. By its means the nature and compositiLon of 

 almost all of the commonly occurring rocks have been determined, and 

 exactly those same features which are of importance in scientific study 



