May 8, 1908] 



SCIENCE 



729 



Beginning and Recession of Saint A'n- 

 thony's Falls: F. W. Sardeson, Min- 

 neapolis, Minn. 



The character of the Mississippi gorge 

 from Fort Snelling to St. Anthony's Falls 

 was outlined and a description was given 

 of the terraces and abandoned gorges, to 

 show that the falls have increased in height 

 during their recession. The early history 

 of St. Anthony's Falls was described in de- 

 tail and the formerly estimated rate of 

 recession of the falls was revised. 



Arched Structure in Lockport Limestone: 

 H. L. Faikchild, Rochester, N. Y. 

 The author exhibited a few lantern views 

 showing arching layers in the Lockport 

 (Niagara) limestone at Niagara Falls. 

 This peciiliar structure has been known for 

 seventy years and was figured in Hall's 

 report on the fourth (New York) district, 

 1843, but no satisfactory explanation of the 

 phenomenon has been found. 



Correlation of Distribution of Copper and 



Diamonds in the Glacial Drift of the 



Great Lakes Region: Oliver C. Far- 



RiNGTON, Chicago, 111. 



The distribution of copper in the glacial 



drift south of the Great Lakes resembles 



closely that of the diamonds which have 



been discovered in the same region. As 



the source of the copper is known to be 



the rocks bordering the shores of Lake 



Superior, it seems probable that the source 



of the diamonds was in the same region. 



The Alteration of Glacial Deposits by Later 

 Ice-in/vasions : Frank Carney, Gran- 

 ville, Ohio. 



The readvance of an ice-sheet subjects 

 the drift already accumulated to gi-ada- 

 tion which probably removes much of it, 

 and to differential stresses which pre- 

 sumably alter the portion not removed. 

 The extent of this alteration is influenced 

 1(1) by the length of the interval of de- 



glaciation, a control that is further condi- 

 tioned (a) by cementation of the early 

 drift, whether till or modified deposits, 

 and (6) by topography; (2) by the thick- 

 ness or weight of the over-riding ice; 

 (3) by the activity of the ice, especially 

 if at different times the predominant mo- 

 tion varied somewhat in direction. The 

 change brought about in over-ridden drift 

 differs with the nature of the drift : if till, 

 the changes produced are disturbance or 

 distortion, foliation, induration, jointing, 

 faulting, and apparently color-alteration; 

 if modified deposits, distortion, jointing, 

 faulting, but only slight foliation and in- 

 duration. 



The presence of such alteration in drift 

 in proximity to drift bearing no such evi- 

 dence suggests that the two represent dis- 

 tinct ice-epochs. 



A Demonstration of the Curvature of the 

 Earth's Surface: Robert M. Brown, 

 Worcester, Mass. 



The paper recortled an observation by 

 the writer on the curvature of the earth at 

 Lake Quinsigamond, near Worcester, Mass. 

 A board two feet square, divided vertically 

 into a black upper surface and a white 

 lower one, was set up with the union of the 

 two surfaces at a certain height above 

 water level. On an island about 4,000 feet 

 away a white bar was erected, parallel to 

 the water and at the height of the hori- 

 zontal line of the first piece of apparatus. 

 In line with these two and about 4,000 feet 

 beyond the second piece, a telescope was set 

 at the given height above the water. On 

 sighting through the instrument the bar 

 was projected against the top of the board. 

 A scale suspended from the bar showed 

 the amount of deviation from a straight 

 line. From this reading the size of the 

 earth was deduced." 



"Printed in full in the National Geographic 

 Magazine, Vol. XVIII., 1907, 771-774. 



