84 bulletin of the 



45th Meeting. April 12, 1813. 



The President in the Chair. 

 Mr. J. B. HiLGARD made a communication entitled: 



AN INQUIRY INTO THE LAWS OE PROBABILITY, 



46th Meeting. April 26, 1813. 



The President in the Chair. 

 Mr. G. K. Gilbert presented a communication 



ON THE glacial EPOCH IN UTAH AND NEVADA. 



(abstract.) 



Ancient glacial moraines and cognate phenomena are known 

 upon the Sierra Nevada as far south as N. lat. 36° 30', and on 

 the Fi^oeky Mountains to nearly the same latitude ; but they are 

 confined to high mountain valleys. The glaciers that produced 

 them did not extend to the lower valleys. There is evidence in 

 the perfect preservation of quaternary and pliocene deposits 

 throughout the intervening "Great Basin," that it was subjected 

 to no general glaciation during the Glacial epoch ; but glaciers 

 existed on the flanks of the highest mountains, and to the list of 

 these the Engineer explorations in 1812 made several additions. 

 The new localities are: White's Peak, Schell Creek range, Ne- 

 vada, N. lat. 39° 15'; Wheeler's Peak, Snake range, Nevada, 

 N lat. 39°; Belknap Peak, near Beaver, Utah, N. lat. 38° 25'; 

 and Fish Lake, Utah, N. lat 38° 30'. The phenomena consist 

 of moraines and moraine lakes, and are found no lower than 8000 

 feet above the sea level. These points are believed to be the 

 most southerly at which, in these latitudes, such traces can be 

 found 



The undrained valleys of the " Great Basin" have been filled, 

 at a recent geological period, by large lakes, of which Great Salt, 

 Sevier, Humboldt, Owens, etc. are the remnants. Mr. Howell 

 and the writer have studied during the past summer the beaches 

 and deposits of the lake that covered the Sevier and Great Salt 

 Lake deserts, and mapped a large portion of its outline. It had 

 an extreme depth of one thousand feet, and an average depth of 

 four hundred. Its length was three hundred and fifty miles, and 

 its area nearly equalled that of Lake Pluron. The mountain 

 ridges, with which the region abounds, studded its expanse with 

 islands, and complicated its shore with peninsulas. Its water 



