BOTANY OF THE ROUTE. 35 



especially west of the Cascade range, the rivers, though small, are exceedingly numerous. 

 Many, too, of quite large dimensions during the rainy season, become nearly or quite dry in 

 summer, particularly cast of the Cascades. Their water is almost always exceedingly clear, 

 though some are turbid during the summer floods, especially the Columbia and Cowlitz, which 

 has then a bluish, milky hue. 



I have seen very few that presented the dark hue arising from decomposed vegetation. One 

 of these is the Okanagan, east of the Cascades, which, unlike all the others on that side, is dark, 

 slow, and broad, having many lakes in its course caused by its expansion. The temperature 

 of this river on September 27 is stated by Lieutenant Mowry as "much higher" than that 

 of the Columbia near its mouth, which was 52°. To this fact I attribi;te the occurrence in it 

 of several interesting species of mollusca, of which I had hitherto found but three species in 

 the rivers. 



Again, on the west side of the range is the Black river, much smaller, though apparently 

 deeper, and perhaps conveying as much water. Around this is the most extensive swamp I 

 have seen in the Territory, partially covered with forest, and doubtless producing many plants 

 not to be found elsewhere. I had no opportunity of collecting anything there. 



It is observable that both of these, as well as the Willamette and that part of the Columbia 

 from the Cascade to the Coast ranges, flow neav\j parallel instead of transverse to the mountains, 

 and, having slow currents, are consequently deeper, warmer, and more expanded than the other 

 streams. In June, 1853, I found the Willamette warm enough to bathe in at Portland, while 

 the Columbia at Vancouver, then high from the summer floods, was entirely too cold. The 

 published record of its temperature during the freshet of 1854 shows that at the commence- 

 ment, on May 8, the temperature of the river at Vancouver was only 40°. It can scarcely be 

 supposed to have been warmer previously, as the rains had not ended nor the weather become 

 hot. From 40° it rose and fell alternately until July 20, when the record terminates, the 

 highest temperature being, on June 30, 55°. It is somewhat singular that the rise in tempera- 

 ture corresponded with the rise of the water, and vice versa during June, which may have been 

 due to warm rains. But as the water fell, during Jul)^ the warmth gradually increased from 

 47° to 53°. 5, the points given for the first and twentieth of the month. It, doubtless, continued 

 to increase afterwards during the lowest stage of the river, which is between July and 

 December. 



It is, however, hardly probable that the warmest portions of the Columbia attain a warmth 

 much above 60°, which is allowing an increase of eight during its course from the mouth of the 

 Okanagan to Vancouver, while it is continually receiving branches from the mountain snows. 

 The temperature of 52°, observed at the former point on September 27, is, doubtless, about 

 the highest it reaches there, since that period was at the very middle of the dry season, and 

 the snow-flood had long since ceased. 



In connexion with this low temperature, and with the fact that in most winters the streams 

 west of the mountains rarely freeze, thus limiting the temperature of the year between about 

 35° and 60°, we find that, though abounding in fish of many species, all those constantly 

 inhabiting it belong to but two famihes, Salmonid^ and Ctprinid^, excluding those which 

 merely enter the river in summer to spawn, as the sturgeon, lamprey, &c. Reptiles and 

 mollusca are also rare, being confined almost exclusively to the lakes, marshes, and sloughs 

 near the river, which become warmer in summer. 



