ISO On the origin of some 



Adding to the above the species from the Devonian of New 

 York and Pennsylvania, described in the Reports of the Geology 

 of those states, and in the Memoir of Goeppert above referred to, 

 we may estimate the known land flora older than the carboniferous 

 period in Eastern America, at about thirty species, belonging to 

 at least fifteen genera, all cryptoganqous or gymnospermous. 



ARTICLE XL — On the origin of some Magnesian and Alumi- 

 nous Rocks, By T. Sterry Hunt, F.R.S., of the Geological 

 Survey of Canada. 



(Presented to the Natural History Society.) 



In common with other observers, I have long since called 

 attention to the fact that silicates of lime, magnesia and oxyd of 

 iron are deposited during the evaporation of many natural waters, 

 such as the mineral springs of Varennes and Fitzroy, and the 

 waters of the Ottawa river. I have also suggested that the sili- 

 cates thus produced may have contributed in a considerable de- 

 gree to the formation of rocks. (^Ainer. Jour. Science, March, 

 1860, p. 284). A hydrous silicate of magnesia which approaches 

 in composition to MgO. SiO^, combined with from ten to 

 twenty per cent of water, and mechanically mixed with small 

 portions of oxyd of iron, alumina, and carbonates of lime and mag- 

 nesia, forms extensive beds with limestones and clays in tertiary 

 strata, in France, Spain, Morocco, Greece and Turkey. It is the 

 sepiolite of Glocker, the meerschaum of some authors, the mag- 

 nesite of others. The quincite of Berthier, which occurs in red 

 particles disseminated in limestone, is a similar compound, con- 

 taining some oxyd of iron. The sepiolite from the basin of Paris 

 occurs beneath the gypsiferous group, and in the lacustrine series 

 known as the St. Ouen limestone, where it forms very fissile 

 shaly layers, enclosing nodules of opal (menilite). The struc- 

 ture of this sepiolite, which I have examined and described as 

 above, and that from Morocco, which is used by the Moors in their 

 baths as a substitute for soap, and has been described by Damour, 

 is peculiar. The mineral is made up of thin soft scales, and 

 when moistened with water, swells up into a pasty mass resem- 

 bliug a finely divided talc. Although agreeing closely with this 

 mineral in the proportions of silica and magnesia, sepiolite con- 

 tains more water, and both before and after ignition is soluble in 



