Upper Part of the Silurian System. 53 



argillaceous substance known as gypsiferous marl, which sui'- 

 rounds these deposits, seem to be due to the precipitation by 

 the carbonate of lime, of the iron and alumina, which have 

 been previously taken up by the water yielding a mixture of 

 these oxides 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 once explain 

 the displacement of the superincumbent materials. The ob- 

 servation 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 carburetted 

 h}drogen, which is copiously evolved by the salines of this 

 region, but it was collected at a time, when, from the minute 

 portion of gypsum in the water, the action seems to have been 

 at an end. I shall not attempt to speculate upon the pro- 

 bable source of the sulphuric acid at present, but shall defer 

 the consideration of the subject, until the publication of my 

 report on the mineral springs of Canada, which will be ac- 

 companied with the analyses of this water as collected in 

 different years. Hoping that my observations may resolve 

 a hitherto unexplained problem in the geology of this region, 

 I beg leave to submit them to the notice of the Association. — 

 American Journal of Science and Arts, vol. vii., No. 20, New 

 Series, p. 175. 



An Account of Two Aerolites, and a Mass of Meteoric Iron, 

 recently found in Western India. By Herbert Giraud, 

 M.D., Professor of Chemistry in the Grant Medical Col- 

 lege, Bombay, Assistant-Surgeon in the Hon. E.I.C.'s 

 Bombay Medical Establishment. Communicated by the 

 Author. 



Although the records of science have of late years abounded in 

 descriptions of meteorites, yet, from their unearthly origin, and cha- 

 racteristic chemical composition, these curious bodies continue to 

 claim the peculiar interest which, it is bnlievrd, may attacii tn two 



