1874 San Diego City Directory
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HEALTH RESORT.
reader is referred. The importance of these tables, especially to physicians and invalids, cannot be overestimated.
A careful perusal and study of them cannot fail to convince the reader that the world cannot produce a country with a more even temperature, nor a place where the invalid is less liable to be chilled by wintry frosts, or debilitated by summer heat.
A daily sea breeze tempers the summer air, and the nigbts are always agreeably cool. It will be observed by reference to the annual table of temperature, etc., for 1873, found in the Appendix, that the prevailing winds in this locality blow from the west and northwest; but this information does not convey a true knowledge of the perfect law or system of our daily ocean and land breezes.
From early morning until 8 or 9 A. M. each day, the velocity of the wind does not exceed two miles per hour, and its direction is variable. As the sun's rays become more vertical, increasing the heat of the earth, which is communicated to the superincumbent atmosphere, gradually expanding it, the air over the water (being much cooler than that over the land), obeying a familiar law of nature, flows to the heated land. As the temperature of the land increases so does the velocity of the wind from the ocean to the land increase, until the greatest heat of the day is attained. This occurs about 2 P. M. The mean of the wind's velocity at this time is about ten miles per hour.
The same law in an inverse order is observed as the sun declines. The regularity of this interchange can be relied upon with nearly the same confidence as the motion of the earth in her daily revolution. This regular ocean breeze each day is the prime cause of our even temperature and equable climate. After sunset the earth soon radiates much of the heat received from the sun during the day, and by 9 P. M. the atmosphere over the land is cooler than the air over the ocean; so that during the night the system of winds is reversed. There are not a dozen days in the year that fog can be seen on land after 9 o'clock in the morning; and it is rarely seen previous to that hour.
The late Prof. Agassiz, whose testimony is worthy of the highest consideration, after spending some weeks in San
