SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 163 



Notes on Structural Materials in Southern California.^ 



BY THEO. B. COMSTOCK, S. D. 



(Read by Title, Section of Geology, Oct. 24, 1904.) 



The use of natural products in buildings, foundations and 

 other structures, of higher class is annually increasing in Los 

 Angeles and the surrounding country, notwithstanding that 

 concrete has also assumed importance from the boldness with 

 which some engineers and architects have recently brought it 

 into service. But concrete itself is only artificial in a secondary 

 .sense. The ultimate constituents are natural mineral products, 

 and one who discusses the subject exhaustively must necessar- 

 ily take into account the deposits of rock from which the com- 

 ponents of cements, mortars and their various combinations 

 are derived. 



In this brief paper it is my purpose to confine attention 

 mainly to some particular features of the local natural supply 

 of ready-made building materials, such as granite, marble and 

 the more commonly used building stones. The elements of 

 <?olor, texture, fracture, mineral composition, and even accessi- 

 bility to market, not to mention just now the durability and 

 suitability in other ways for structural use — all these features 

 Jiave been dependent upon geologic history. That is to say, 

 the geographic distribution, topographic outlines, exposure for 

 working, form of blocks in a given quarry, and the appearance 

 and wearing qualitj^ of the rock, as well as the response to 

 tooling and polishing, are not mere chance results. These vary 

 exactly in accordance with conditions antecedent, which can 

 readily be determined and quantitatively estimated by the 

 practical geologist from observations in the field. 



A prominent firm who supplied rock upon a contract in Los 

 Angeles started upon the delivery without knowing that their 

 quarry Avould furnish the needed stint. This risk of loss by 

 failure to comply with their agreement was wholly unneces- 

 sary, because a competent geologist could have settled the 

 matter beforehand with moderate study of the ground. There 

 are also certain well-established facts which enable one familiar 

 with the details to determine readily whether any given supply 

 of rock will become useful in the arts. For instance, a grade 

 of marble which is somewhat popular here, although it seriously 

 offends the taste of others, was examined some time ago by 

 the writer and the result of weathering considered dubious. 



■There is room onlv for an abstract here. 



