No. 5.] NATURAL HISTORY SOCIETY. 311 



their mineral coostituents, and although they may have passed 

 over a different class of rocks in their approach to this aflfluence, 

 the points of difference in their character are not remarkable, 

 and are well calculated to produce a mingled water of a more 

 potable character than either would be separately. 



The leading feature of the Assiniboine water is Sulphate of 

 Magnesia, which is not present in tha Red River water, but is 

 partially replaced by iron, giving it a slight and temporary 

 chalybeate character. 



This often occurs in Derbyshire, England, where the water 

 passing over an ochre bed becomes turbid and red from the 

 presence of iron, after which the water clears again, deprived of 

 much of its bittern, viz. magnesic salts. This would be precipi- 

 tated by ferric or alkaline carbonates and by soluble phosphates, 

 and a perfectly sweet water obtained. It is quite probable that 

 the Red River water has thus had its magnesic salts removed, 

 and its iron and lime carbonate proportionately increased by the 

 minerals which it has passed over in its course, and by this 

 means it has been rendered potable and sweet, although slightly 

 chalybeate. Artificial filtration might accomplish the same 

 result for the Assiniboine water. 



Principal Dawson presented the following list of the land 

 shells of Prince Edward Island by Francis Bain, Esq. of North 

 River, P. E. I. : 



Helix (^Patula) striatella, Anthony. 



* Helix (^Zonites) arborea, Say. 

 Helix (^Z.) ferrea, Morse. 



* Helix (^Z.) chersina, Say. 

 Helix ( V'llloiiicz) miniUa, Say. 

 Helix (^Helicodiscus) lineata, Say. 

 Vitrina liiJipida, Gould. 

 Succinea Totteniana, Morse. 

 Succinea ovalis, Gould. 



Zua (^Ferussaceici) liibricoides, Stimpson. 

 Zoogenetes (^Acanthinula^ harpa, Say. 

 The species marked thus *, and also Helix ( Tachea) hortensis 

 Miill (the yellow variety), have been noticed in Dawson and 

 Harrington's Report on the Geology of Prince Edward Island. 



The stouter shelled species are all something smaller than the . 

 same occurring in the New England States ; but these with very 



