23 8 



NINTH ANNUAL REPORT OF 



They are nearly always aUended with a sky of cloudless blue. Those 

 from northwest to southwest are cold and chiUing at all seasons, and in 

 summer loaded with the ocean mists. But they do not often produce 

 rain. The coast winds from south and southeast are most conducive to 

 rain, and they are always warm. The course of the winds in relation 

 to rain will be considered under the head of rains. 



The force of the w^inds at ditterent periods of the day, and Irom dif- 

 ferent points of the compass, is a subject of some interest. It is repre- 

 sented by figures — indicating calm or nearly calm, 1 a light breeze, 2 

 a moderate breeze, 3 a strong breeze or wind, 4 a high wind, and 5 a 

 very high wind. The observations occupy three columns, for the fore- 

 noon, atternoon, and evening. The mean of each of these columns for 

 every month is given in the following table, and the fourth column con- 

 tains the mean of the three observations, collectively, for each month. 



January . . 

 February.. 

 March . . . 



April 



May 



June 



July 



August . . . 

 September 

 October . . 

 November 

 December 

 1851. . 



Forenoon. 



Afternoon. 



Evening. 



.66 

 1.07 

 1.40 

 1.33 

 1.61 

 1.92 

 2.19 

 1.77 

 1.28 

 .87 

 .70 

 1.07 

 1.32 



Mean. 



1.11 

 1.48 

 1.77 

 1.73 

 2.00 

 2.19 

 2.27 

 1.96 

 1.71 

 1.26 

 .92 

 1.25 

 1.64 



The reader will perceive that the average force of the wind in the 

 afternoon was greater than in the forenoon, in every month of the year 

 except December. By referring to my Philadelphia tables, I find there 

 is no uniformity in this respect, the morning winds being stronger in 

 some months, and the afternoon winds in others. 



The evening winds were uniformly lighter than the afternoon, and 

 lighter than those of the forenoon, except in the three summer months, 

 when they were decidedly stronger than in the forenoon. At Philadel- 

 phia the evening winds sum up lower in strength than those of the fore- 

 noon or atternoon, in every month, without exception. 



The table shows a remarkable progressive increase in the force of the 

 atmospheric currents from January to July, the latter being the most 

 windy month of the year ; and then a decrease till November, the 

 calmest month. At Philadelphia there is no such regularity. Autumn 

 is the calmest season at both places, but summer comes next in the At- 

 lantic States, then winter, and lastly spring, which is the windiest sea- 

 son on the eastern side of the continent. 



From May to September, inclusive, there is more wind at San Fran- 

 cisco than at Philadelphia; but in the remaining five months, from Oc- 

 tober to April, there is less. 



Not only in regard to time do the winds from the western semicircle 

 greatly preponderate, but also in force. The land winds are often very 



