284 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



would not have precluded intermigration, for salmon are known to 

 travel more than 2,000 miles up the Yukon to spawn. 



II 



By the time Lake Uinta had become thus well stocked with fish it 

 was a mature lake, for it had already been in existence more than a 

 miUion years. Now as lakes grow old they, Uke men, acquire stores 

 of worldly goods. So it was with Lake Uinta; as it advanced in age 

 its waters became increasingly rich in foodstuffs. And, like a benevo- 

 lent monarch, the lake gave all this increasing wealth for the good of 

 its subjects — the varied and extensive aquatic population. 



The life of a populous lake is a complex society, the members of 

 which are interdependent. Most elemental are the microscopic plants 

 and animals that float freely in the surface waters and derive their 

 nourishment and energy directly from the sunlight and the dissolved 

 salts. Upon the abundance of these minute creatures depends the 

 very existence of other life in the community, for they are the ultimate 

 source of food. Successively larger animals — the fairy shrimp, the 

 water Ilea, and the higlily mechanized wheel animalcules — feed upon 

 them and in turn are fed upon by small fish. 



At this mature stage of Laj^e Uinta these tiny specks of life found 

 themselves in a congenial environment, where food abounded and the 

 temperature was most agreeable. They flourished in the midst of 

 plenty and, late in the summer, when the water had been thoroughly 

 warmed, literally took possession of the lake. Their numbers in- 

 creased at an astounding rate; they clouded the water, then turned it 

 a fulvous green, and finally covered it with a green scum, wliich the 

 wind parted into lanes where the water might ripple again and reflect 

 the blue of the sky. From beneath this surface stratum, filled with 

 life, those organisms that had grown weary of the struggle for exist- 

 ence floated gently downward and sought rest in the quiet depths. So 

 vast was the number of these weary motes that, despite their micro- 

 scopic size, they bulked large in the total volume of sediment that 

 reached the lake bottom. Indeed, these late summer epidemics gave 

 rise each year to a distinct dark layer of organic substance. It was 

 partly by means of these organic layers that the ancient lalvc recorded 

 the passing of the years. But there would have been nothing to mark 

 one layer off from another formed the following year or the year be- 

 fore, if it had not been for a different land of sediment, which accumu- 

 lated more or less continuously throughout the year. 



Streams brought to the lake not only fine mineral particles in 

 suspension but also the elements of other minerals in solution. Those 

 particles that rode in on the streams' turbulence found nothing 

 buoyant in the quiet lake and hence settled placidly to the bottom. 

 But the elements in solution were dispersed through the whole water 



