of Oregon and Upper California. 389 



wooded about Astoria, — only the hills or mountains near Francis- 

 co, — and not even the loftier ridges in the Peninsula of Califor- 

 ma. Lines of equal forest growth — supposing (he surface at a 

 corresponding level and uniform throughout — would very slowly 

 diverge from the coast as we follow them north in California, a 

 little more rapidly in southern Oregon, and still more so to the 

 north of the Columbia: such lines would curve, as we have 

 reason to believe, with a regularly varying curvature. 



Exceptions to 'such regular courses in these lines necessarily 

 proceed from inequalities of surface, the varying direction of the 

 coast, and from the moisture of springs in low lands. It is also a 

 common fact that where hills of five to eight hundred feet are bare 

 of trees throughout, those of twelve hundred will be wooded to 

 their bases, owing to the moisture which these higher ridges 

 condense to be thence carried down the slopes. 



V. Climatal cause of the distribution of forest and prairie re- 

 gions. — The peculiarities mentioned, run parallel with other facts 

 relating to the climate: and the parallelism is so exact, that we 

 cannot fail to recognize the cause of the former in the latter. A 

 full series of meteorological observations for the territory has not 

 yet been made. But it is sufficient for the present purpose to 

 know that the rainy season in the Willammet (lat. 45° to 46°) 

 continues through five to seven months, the colder months of the 

 year; while on the lower Sacramento — about latitude 38° — it 

 is usually confined to three or four months. The rains ceas- 

 ing, the grass dries up in the course of the following one or two 

 months, and remains as dry fodder for the cattle through the rest 

 of the year, the juices being retained in consequence of the 

 completeness of the drought. This was the condition of the 

 plains when traversal by the writer in August, September and 

 October of 184L In Oregon in the month of August, the lofty 

 cones of St. Helens and Mt. Hood, though piercing far into the 

 region of perpetual snows, were un obscured to their summits 

 standing as natural hygrometers, indicating the dryness of the 

 season at every height to 15,000 feet. There was occasionally a 

 light haze in the atmosphere, but rarely a cloud. This is widely 

 different from the condition of the much lower mountains cf 

 Eastern America. There was no rain during the journey from 

 Vancouver to Francisco. The remarks here made apply partic- 

 ularly to the region between the Cascade and Coast Mountains, 

 or over thirty miles from the sea. 



Within the Coast region, where forests prevail, the mists of 

 summer are frequent and extremely copious, almost or quite 

 amounting at times to rain. On ascending the Columbia, wc 

 passed abruptly about forty miles from its mouth, from a region of 

 dense fog, to sunshine; and looking back, the mist seemed to 

 stand like a high barrier across the country. The same is the 





