380 ASSINJSTB0INE AND SASKATCHEWAN EXPEDITION. 



tious grass, called buffalo grass (Sysleria dyctaloides). 

 A narrow strip of alluvial soil, supporting a coarse grass 

 and a few cotton-wood trees, marks the line of the water- 

 courses, which are themselves sufficiently few and far 

 between. 



" Whatever may be said to the contrary, these plains 

 west of the 100th meridian are wholly unsusceptible 

 of sustaining an agricultural population, until you reach 

 sufficiently far south to encounter the rains from the 

 tropics. 



" The precise limits of these rains I am not prepared 

 to give, but think the Eed Eiver (of Louisiana) is, perhaps, 

 as far north as they extend. South of that river the 

 plains are covered with grass of larger and more vigour- 

 ous growth. That which is most widely spread over the 

 face of the country is the grama or mezquite grass, of 

 which there are many varieties. This is incomparably 

 the most nutritious grass known."* 



AURORAS. 



On the night of October 2nd, when camped on Water- 

 hen Eiver, an Aurora of unusual brilliancy and character, 

 even in these regions, surprised us with the varied mag- 

 nificence of its display of light and colour. A broad ring 

 of strong auroral light nearly encircled the Pole Star. It 

 possessed an undulatory motion, and continually shot 

 forth, towards and beyond the zenith, vast waves of faint 

 light. They followed one another like huge pulsations — 

 wave after wave — expanding towards the south with un- 

 diminished strength, and continuing many minutes at a 



* Report on the United States and Mexican Boundary Survey, made 

 under the direction of the Secretary of the Interior, by William H. Emory, 

 Major First Cavalry and United States Commissioner. Washington, 1846, 

 pp. 43-47. 



