662 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



over the land to ascend; the place of this air must be filled from some- 

 where as the denser and colder air of the ocean flows in which makes the 

 sea breeze. About ten miles from San Francisco, or even on the east side 

 of the bay, this sea breeze fails entirely. There are several valleys scat- 

 tered along the east side of the bay by which the breeze is tempered, 

 making the most delicious climate in the world. For the purpose of sleep, 

 San Francisco is exceedingly pleasant as the summer nights are cool ; never 

 too warm to do without blankets. Farmers sow their barley and wheat in 

 the fall so as to get them started in winter as there is no rain in summer. 

 Another singular feature about San Francisco is that a distance of fifty 

 miles, in any direction from it, brings you into a different climate. In win- 

 ter the rains are southerly and the winter season generally is very much 

 like our Indian summer. A residence of some five or six years there war- 

 rants me in saying that it is the most pleasant climate on earth. 



Dr. R. P. Stevens. — The experiments made during the balloon ascents in 

 the vicinity of London, demonstrated what had been partly proven before, 

 that there are different strata of air and that each has a different temper- 

 ature. In deducing the laws of meteorology, I suppose we have done as 

 much, if not more on the continent of America, than any other portion of 

 the globe. The Canadian meteorologists have been in close communica- 

 tion with those of the United States, and since the Smithsonian institution 

 was founded their observations have been monthlj compared. The inves- 

 tigations of Redfield and Hare have demonstrated that all the great storms 

 that pass over the American continent are westwardly; that our northeast 

 storms are but the preceding winds of an immense westerly storm; and 

 that these westerly storms are preceded by a fall in the barometer. Some- 

 times these storms pass in straight lines and sometimes in curves. Great 

 changes in the temperature are produced by the cold air from the west 

 descending and carrying the moist air before it, which passes along the 

 great mountains of the west and becomes colder by expansion, and when 

 it becomes dry, acts as a non-conductor between the earth and sun, pre- 

 venting the rays of heat from being absorbed by the ground. The westerly 

 storms are the mighty ones, and from this region, I may safely say, all our 

 great storms invariably come — for whoever heard of a tornado coming 

 from the east ? I now speak of hurricanes which sometimes spread a thou- 

 sand and sometimes only a few miles in width. The great tornado in Ar- 

 kansas some few years ago, was preceded by a westerly wind, and extended 

 about six rods in width. These storms move in cycloids, and wherever the 

 centre of these cycloids are there the storm will be the most violent. Prof. 

 Espy's theory is that the warm air coming from the tropical regions when 

 moving over the land becomes heated and passes upwards, and meeting 

 with a cold stratum of air it precipitates its moisture in the form of snow 

 or rain, and just in proportion to the rapidity of the ascent and the area 

 of the rising column of heated air, other things being equal, is the extent 

 of the storm; so that if the North American continent was one great plain, 

 the foretelling of a storm and the latitude in which it would prevail, could 

 be easily foretold; but owing to our large rivers, valleys and mountains, 

 our calculations are not so certain. In the village of Hudson, on the 

 Western Reserve, Ohio, when the dew point indicates a rapid evaporation 



