



Acid Springs and Gypsum of the Onondaga Salt Group. 177 



deposits, is confirmed by the common experience of the people 

 of Western New York, where it is a well known fact that since 

 the settlement of the country, walls have been disturbed and 

 houses raised from their foundations by a gradual elevation of the 

 surface, where subsequent examination has shown the presence 

 ot domes of gypsum. 



On comparing these facts with those observed in connection 

 with the acid spring, it appears probable that the origin of the 

 gypsum is to be ascribed to the action of such mineral waters 

 upon the calcareous strata. How far the pressure at a great depth 

 may operate in preventing chemical changes, we may not know, 

 but it is easy to see that once coming to a situation where it 

 could act upon the limestone, it would evolve carbonic acid gas, 

 and form a calcareous sulphate which from its sparing solubility 

 would be at once deposited in a crystalline form, while the water 

 would pass off saturated with the sulphate, and at the same time 

 carrying with it the soluble sulphates of magnesia, alumina, and 

 iron, which would be formed from the other bases, generally pre- 

 sent in the limestones of this region. If the amount of acid 

 were copious, or the supply of calcareous matter limited, the 

 water might rise to the surface with free acid, as in the cases al- 

 ready noticed, and when the deposition of calcareous sulphate 

 had extended so far as to protect the carbonate from farther action, 

 the water would appear with a much smaller portion of bases 

 than before, baring only the sulphate of lime which it could dis- 

 solve from the sides of its channels. 



If on the contrary, the acid were entirely neutralized, the sprin o 

 would present at the surface the character of an ordinary bitter 

 saline, containing calcareous and magnesiavi sulphates; two springs 

 °f this character are indeed found in the same formation not far 

 from here. The ferruginous and argillaceous substance known 



b 



as gypsiferous marl, which surrounds these deposits, seem to be 

 due to the precipitation by the carbonate of lime of the iron and 

 ■tamtoa, which have been previously taken up by the water yield- 

 in g a mixture of these oxyds with carbonate and sulphate of 

 lime. The fact that crystalline gypsum occupies nearly twice 

 the space of an equivalent quantity of carbonate of lime, will at 

 °nce explain the displacement of the superincumbent materials. 

 The observation which is now required to confirm this theory, is 

 to find the carbonic acid which should be evolved from the de- 

 composition of the limestone, actually disengaged from one of 

 these springs ; the small .quantity of gas which rises from the 

 Tuscarora spring was found to be principally carburet ted hydro- 

 gen, which is copiously evolved by the salines of this region, but 

 it was collected at a time when from the minute portion of gyp- 

 sum in the water, the action seems to have been at an end. I 

 shall not attempt to speculate upon the probable source of the 



Second Series, Vol. VII, No. SO, March, 1849. 23 



