T314] BUILDING STONES— WATERS OF THE TERTIARY. 1S7 



The localities thus far observed of the sandstones and claystones 



of the Siliceous Claiborne stage, have been mentioned above ("'188, 



190 2 ). 



These rocks are generally very durable, where they are not too 

 soft from the lirst. 



The limestones of the calcareous Tertiary, some of which are of 

 excellent quality as building stones, have been spoken of above 

 (f 304 to 414). 



The gray and white sandstones of the Grand Gulf Group, whose 

 chief localities of occurrence have already been given, (232 to 236 ; 

 242). would, so far as their obvious physical properties, their fre- 

 quency of occurrence, and their mass is concerned, form a very 

 eligible and highly valuable building material, but for the draw- 

 backs already referred to (11231), viz : their want of durability 

 when exposed above ground. 



In numerous instances their gradual softening has been owing, no doubt, to 

 the amount of salts they contain, which in some regions (Campbell's Creek, 

 Steen's Creek, Rankin county, 1241). continually effloresce on their surface, 

 and finally reduce them to powder. In others, however (and particularly at 

 the Capitol at Jackson), the chief cause of their decay has been the presence of 

 small concretions of iron pyrites, whose oxidation or vitriolescence causes partly 

 rusty spots, which, though soft :r than the rest of the mass, serve mainly to 

 mar the appearance of the surface ; partly, by the swelling consequent upon this 

 process, breaks out fragments, and rends open large sized blocks ; thus serious- 

 ly endangering the security of buildings. The acrid, inky taste of the spots 

 where this process is going on, will readily show to any palate the presence of 

 copperas. 



Two simple practical rules to be observed in the use of this rock, result from 

 the above considerations. Firstly, the use of any rock or portions of rock, 

 where the brilliant, golden-yellow particles or lumps of the iron pyrites may be 

 observed, or where on surfaces naturally exposed, the rust spots indicate its 

 presence, ought to be strictly avoided. Secondly, the rock when used ought to 

 be protected against the action of fir and moisture, by a good coating of linseed 

 oil, soluble glass, varnish or the like ; and the same means may be employed 

 to arrest the process of decay where it has already commenced. — It also 

 follows, that when the rock is used in works little exposed to the action of the 

 atmosphere, and changes from wet to dry (as in foundations, etc.), there is less 

 danger of a change in its mass. 



314. Waters of the Tertiary Formations. — a. Waters of the 

 Lignitic Groups. — It is but rarely that waters derived essentially 

 from the strata of any of the lignitic stages of the Tertiary, 

 possess that degree of purity which would characterize them as " free- 

 stone waters.'' Those derived from the materials of the Grand 

 Gulf Group are almost without exception, mineral waters proper ; 

 i. e. sufficiently strong to be recognized at once by the taste, and in 

 the majority of cases, unfit for constant and daily use. In a less 

 degree in general, this is the case also with those derived from the 

 Lower or Northern Lignitic Group, and from the minor lignitic 

 stages of the Tertiary generally. It is, ordinarily, only where 

 yellow sands enter largely into the composition of the strata of the 

 Northern Lignitic Group (as is the case most frequently where 



