278 FOSSIL FOOD 



they have even invented a definite name, Lake Bonneville, 

 occupied a far larger valley among the outliers of the 

 Rocky Mountains, measuring 300 miles in one direction by 

 180 miles in the other. Beside this primitive Superior lay 

 a second great sheet an early Huron (Lake Lahontan, 

 the geologists call it) almost as big, and equally of fresh 

 water. By-aiid-by the precise dates are necessarily in- 

 definite some change in the rainfall, unregistered by any 

 contemporary ' New York Herald,' made the waters of 

 these big lakes shrink and evaporate. Lake Lahontau 

 shrank away like Alice in Wonderland, till there was 

 absolutely nothing left of it ; Lake Bonneville shrank till 

 it attained the diminished size of the existing Great Salt 

 Lake. Terrace after terrace, running in long parallel lines 

 on the sides of the Wahsatch Mountains around, mark the 

 various levels at which it rested for awhile on its gradual 

 downward course. It is still falling indeed ; and the plain 

 around is being gradually uncovered, forming the white 

 salt-encrusted shore with which all visitors to the Mormon 

 city are so familiar. 



But why should the water have become briny ? Why 

 should the evaporation of an old Superior produce at last 

 a Great Salt Lake ? Well, there is a small quantity of salt 

 in solution even in the freshest of lakes and ponds, brought 

 down to them by the streams or rivers ; and, as the water 

 of the hypothetical Lake Bonneville slowly evaporated, 

 the salt and other mineral constituents remained behind. 

 Thus the solution grew constantly more and more con- 

 centrated, till at the present day it is extremely saline. 

 Professor Geikie (to whose works the present paper is much 

 indebted) found that he floated on the water in spite of 

 himself ; and the under sides of the steps at the bathing- 

 places are all encrusted with short stalactites of salt, pro- 

 duced from the drip of the bathers as they leave the water.. 



