BUILDING STONES. 173 



Limestones.] 



though the thickness of the bedding at individual quarries is an element 

 that is very indefinite, and -varies according to the length of time the rock 

 has been exposed to the weather, and the depth to which the excavation 

 has been carried. The heaviest beds now wrought were split into several, 

 much thinner, when the quarries were first opened, but as the work has 

 progressed the thin beds have gradually become consolidated. The quar- 

 ries near the state capitol, owned by Messrs. Breen and Young, M. Roche, 

 and Win. Zollman, were opened in 1856, and have been in uninterrupted 

 use ever since. Those of Win. Dawson in West St. Paul, were begun in 

 1S5S, those of the Fort street road in 1870, and those on Dayton's bluff in 

 1869. Mr. Gotzian's quarries on Dayton's bluff were opened in 1870. 



As has already been stated under the head of dolornitic limestones, this 

 rock contains a considerable amount of bluish, shaly matter coarsely dis- 

 seminated throughout even the calcareous layers, rendering it an inferior 

 building stone. For that reason it is not now generally employed in first- 

 class structures, except in the foundations and inner walls where it is pro- 

 tected from disintegration under the weather. The stone itself has an 

 attractive and substantial aspect, when dressed under the hammer the 

 variegations due to the alternating shaly and limy parts giving the face a 

 clouded appearance as of gray marble, without being susceptible of a uni- 

 form polish. When protected from the weather the shale will endure and 

 act as a strong filling for the framework of calcareous matter for a long 

 time; but under the vicissitudes of moisture and dryness, and of freezing 

 and thawing, it begins to crumble out in a few years. This result is visible 

 in some -of the older buildings, both in St. Paul and Minneapolis, and has 

 provoked a very general inquiry for some suitable substitute in those cities. 

 The natural color of the stone, on deep quarrying, is blue, but it is often 

 faded to an ashen drab to the depth of several feet, depending on the ease 

 with which water and air find access within. The porous layers are apt to 

 be most faded. The long- weathered surface is of a light-buff color, or if iron 

 be present in dripping water, or contained in the stone as pyrites, so sit- 

 uated as to be oxydized, the color is sensibly deepened to a rusty yellow, and 

 at the same time the stone is rendered more enduring on account of the 

 irony cement. The protoxide of iron, also, which is in the shale, and con- 

 stitutes one of the elements of weakness in the rock, is changed to a per- 



