Biological Institutions 79 



banks, and the stronger the wave action, the more ch-arly 

 marked will the terrace be. AVhen, on the other hand, llic 

 lake is receding;, the terraces will be wanting or ill-deliiicd, 

 and the shores gradually sloping. Thus a series of terraces, 

 in an old lake basin, with intervening slopes, means a suc- 

 cession of alternating wet and dry periods in the past, during 

 the former of which the water supply was sufficient to main- 

 tain the lake at a constant level, while during the latter the 

 level was steadily falling. Still further evidence may be 

 obtained from submerged forests. The bottom of Stump 

 Lake, N. Dak., at one time part of the much larger glacial 

 lake, Minnewaukon, was years ago covered by a forest, as is 

 evidenced by the stumps, many (f which are still lying 

 on the old lake bottom, now being exposed by the progressive 

 shrinkage of the lake from excessive evaporation. This 

 forest contained trees probably very similar to those at present 

 growing about the lake shore. Thus, within comparatively 

 recent times,^ Stump Lake was successively part of a con- 

 siderable body of water, then dry land (at least in part, the 

 extent of the submerged forest not being known) for a suffi- 

 ciently long period to allow of the growth of forest trees of 

 considerable size; again it became a lake submerging the 

 forest and now for the second time it is disappearing. This 

 evidence is borne out by terraces beneath the present lake 

 level and by piles of boulders in the lake which show evidence 

 of the work of ice in their formation. 



And so Professor Huntington and his colleagues have 

 called npon Pyramid and Winnemucca Lakes, in western 

 Nevada, remnants of the old glacial Lake Lahontan, and 

 Owens and Mono Lakes in California to testify ; and their 

 evidence has supported that of the "big trees," and the words 

 of earth and tree have in their turn been verified by the pages 

 of history. According to the evidence it is about 2,000 years 

 since these lakes had an outlet, so that during the Christian 

 era they have been gradually shrinking, oscillating up and 

 down with the varying rainfall of the centuries. 



"The lakes do more than indicate a change of climate 

 within two or three thousand years. They also show that the 

 change has been highly irregular. This is proved by a large 

 number of strands lying below the level of the outlets, and 

 by the way in which these vary in character and in the extent 

 to which they have been covered by fresh detritus washed 

 down from the mountains. At Owens Lake there are four 

 series of strands. These apparently correspond to the four 

 chief periods when the climate has grown moist as shown by 

 the growth of the big trees. , . . Fortunately, Owens Lake 



* Since the Glacial Epoch. 



