ACADEMY OF SCIENCES. 113 



eral features of oiu- climate in ordinary years, but in those seasons in M^Iuch the 

 Equatorial and Polar currents run in broad belts, \ve either have a very dry 

 season when wholly within the northern current, or a warm, moist season when 

 in the southern current, or, such is the extent of our State in latitude, that one 

 portion of it can be within the Polar current and another portion within the 

 Equatorial current during the greater part of the winter, and then we have 

 rains in one part of the State and drought in another part. 



A rough sketch of the weather during the present winter, not only in this 

 State but across the continent, will afford an illustration of the prevalence of 

 these opposite currents over a large extent of country, and the character of the 

 seasons depending on them. The accompanying diagram will illustrate the 

 tracts of country over which these different air-currents prevailed. About the 

 middle of October we had a portion of the Equatorial current in the northern 

 part of the State, but previously to this the current had been blowing over 

 Oregon and Washington Territory, causing very heavy rains there in September 

 and the earlier part of October. After this we had nothing like a southerly 

 gale until February ; but during most of this time, and particularly during the 

 earlier part of the winter, the Equatorial current was blowing at a distance of 

 three or four hundred miles from the coast, and was impinging on the coast of 

 Oregon. Almost every ship that arrived in the harbor during November and 

 the earlier part of December, reported having experienced very heavy weather 

 at some distance from the coast, to the westward and about the mouth of the 

 Columbia, north of us. One ship towards the middle of December reported 

 being caught in a cyclone, in which the barometer fell to 28. 54 in., said to be 

 the lowest point ever reached by the barometer on these shores. During the 

 whole of this period, or from October until February, almost the entire State 

 was under the Trade or Polar current ; the southern part of the State com- 

 pletely so, whilst in the northern and middle portions of the State occasional 

 eruptions of moist air broke in from the northward and westward, giving us 

 light fog-rains and a great deal of foggy weather. These rains were partial and 

 very different in their chai-acter and distribution from the true rains of the fully 

 established Equatorial current. They were heavier along the coast, particularly 

 towards their southern border, where the western current seems to have been 

 entirely kept back from the interior by the coast range of mountains, no rain 

 falling in the Salinas Valley, although on the mountains on the western side of 

 the valley there were copious showers. As these partial currents passed to the 

 eastward less rain fell (at Sacramento 6.8 inches to 11 inches in San 

 Francisco, and still less in the mountains), the very reverse of what takes place 

 in a rain from a full Equatorial current, when the rainfall is always greater in 

 the mountains. While this has been the state of the weather during the greater 

 part of the winter in this State, we find that to the eastward as far as Omaha 

 this same northerly current has generally prevailed^ — at least concluding such to 

 be the fact from the absence of snow in the interior of the continent — whilst 

 again to the east of this, and extending to the Atlantic coast, a warm Equatorial 

 current has prevailed since October, when its irruption was marked by excessive 

 rains, causing great damage. This current seems to have maintained its 



