VOT.. I.] Proceedings of Societies. 317 



important to know that a disturbance in the atmosphere of the nature of a storm 

 necessitates, at the place of origin, a plentiful supply of heat and moisture. These 

 two elements comprise the food of a storm, and without them cyclonic development 

 is impossible. As any cyclone embraces an area of from 500 to 1,000 miles in di- 

 ameter the source of food supply must be of proportionate extent and permanency. 

 The breeding-ground must have capacity to incubate and invest with moving power 

 a continued succession of enormous atmospheric eddies. Therefore, in solving the 

 weather problem of any region we must first locate its source of cyclonic develop- 

 ment and supply. In the northern hemisphere there are only two such places of 

 origin, viz., the Japan current of the North Pacific and the Gulf and Gulf Stream of 

 the North Atlantic. The distribution of temperature and precipitation over any 

 region is intimately dependent upon the peculiarities of cyclonic movement for that 

 region. This is especially true of precipitation, and therefore the frequency and 

 latitude of the easterly movement of cyclonic areas from the Pacific Ocean, over 

 North America, is the keynote to the conditions which control the occurrence of 

 rainfall in the Pacific Coast States. Some of these storms have been traced directly 

 from the Japan Islands and all from the Japan current. The typhoon of the China 

 and Japan seas may become the violent cyclone which sweeps the coast of Oregon 

 and Washington with great fury. The course of these storms is northeastward 

 from the Asiatic coast to Behring Sea; thence curving southeastward to the coast 

 of British Columbia and Washington. In some instances they cross over the south- 

 ern portion of Alaska, or at points between Alaska and British Columbia. The 

 period of greatest frequency and intensity of the North Pacific cyclones coincides 

 with the occurrence of the "wet season" in California. This season is more depend- 

 ent, however, upon the latitude of the easterly movement of the cyclones. The 

 ** wet season " includes the month of November to March, inclusive, and occasional 

 heavy rains occur in October and April, There will be striking variations in the 



amount of rainfall during this season in different years, dependent solely upon the 

 southerly movement of the cyclonic areas. Heavy rains can only occur in Califor- 

 nia where the cyclonic movement is southeastward through Oregon. When the 

 storm center reaches southward into the northern portion of California and Nevada 

 the heaviest precipitation will occur south of the 42d parallel. To understand the 

 distribution of precipitation attendant upon any cyclone we must know the peculiar 

 characteristics which attach to each of the four quadrants of a cyclonic area, a sub- 

 ject which there is not space to discuss in this paper. 



The remarkable rainfall in California during October, 1889, illustrates the effect 

 of the southerly trend of cyclonic areas in augmenting the rainfall south of the 42d 

 parallel. During that month the precipitation exceeded the normal from two to 

 thirteen inches, and was the heaviest for the month in a period of forty years. An 

 examination of the storm-track charts for that month shows that all of the cyclones, 

 except two, passed eastward through central Washington and northern Oregon, 

 and one extended southward into the northern portion of California and Nevada, 

 In previous Octobers the storm centers had passed eastward along the northern 

 boundary of Washington, and in most instances considerably north of that State. 

 This was the case during the dry Novembers of 1S62, 1876, 1884 and 1890, and ex- 

 plains other dry periods during the "wet season." 



An explanation as to why cyclonic areas trend further southward in winter than 



