242 THE POPULAR SCIENCE MONTHLY. 



hundred to five hundred feet, and then unconformably overlaid by 

 the orange sand a deposit coeval with the glacial drift. Borings in 

 lower Louisiana show first the Port Hudson group or post-glacial de- 

 posits ; second, the orange sand ; and, third, the underlying eroded 

 Tertiaries with their characteristic fossils. This excavation could not 

 have been made unless the waters of the Gulf had been at least five 

 hundred feet lower than at present. 



Other facts further illustrate these former elevations. Upon the 

 Atlantic border between New Orleans and New York we find a low, 

 broad plain, largely consisting of marshy or drowned lands. On reach- 

 ing Virginia this land begins to disappear, but the plain holds the 

 same relation to the continent, as it continues to exist in the subma- 

 rine banks east of Massachusetts. Curiously enough, we now dredge 

 from the George's and Great Banks Tertiary fossils similar to those 

 occurring in the unsubmerged parts of this plain. Their existence 

 beneath the ocean had never been suspected till the possible identity 

 of the Atlantic plain with the eastern shoals had been suggested, sub- 

 ject to the crucial test of dredging. 



These facts authorize us to believe that the eastern half of the 

 continent has been elevated certainly six hundred feet in the glacial 

 period. As this elevation included Northern Europe, and consequent- 

 ly the polar districts, so as to unite the Old and the New Worlds, we 

 may be able to follow the older writers, and find in this land-mass the 

 conditions adequate to produce the glacial cold. Such a cause will 

 explain the facts more satisfactorily than the invocation of the eccen- 

 tricity of the earth's orbit, or the precession of the equinoxes. If we can 

 combine the two classes of causes, we can certainly explain all the phe- 

 nomena, besides obtaining the data for the chronology of the ice age. 



The Melting op the Glacial, Sheet. Time fails us to describe 

 the marvelous facts connected with the melting of the ice. The nu- 

 merous kames, elevated sand-plains, and river-terraces, found every- 

 where in Northern America, came into existence with the copious 

 floods of water resulting from the dissolution of the ice. The history 

 of the ice age is incomplete without a discussion of the events occur- 

 ring in this great continental freshet ; but this sketch must be deferred 

 for the present. 



-4--~0- 



AN EXPEEIENCE IN SCIENCE-TEACHING. 



By STANLEY M. WARD. 



TT^OR the past two years I have had charge of a public school in 

 -L Pennsylvania, and have endeavored to awaken in the minds of 

 my pupils a love for and an interest in science, with especial reference 

 to the truths and lessons of physiology and zoology. Perhaps my 



