1819.] Days of Rain, Snow, and Drizzle, at Viziers. Ill 



is much greater than that of May. We see from this that the 

 minima correspond nearly to the coldest and hottest seasons of 

 the year, and the maxima to the mean temperature of the 

 year.* 



During the course of these 40 years, the most rainy has been 

 1801 ; in which there fell 48 inches and 1 line of water; and 

 there were 141 rainy days. The driest was 1779, in which there 

 fell only 20 inches 7-i- lines of water, and in which there were 

 only 69 rainy days. 



If we add the quantities of rain which fell during every decade 

 of these 40 years taken separately, and divide the sum by 10, to 

 have the annual mean for each of these four decades of years, 

 we shall obtain the following quantities : 



Decades of years. 



Quantity of rain fallen during 

 eath decade. 



Mean annual quan- 

 tity of rain. 



Lines. 



In. 

 31 

 33 



34 

 37 



1 i u 

 9» o 



- i j"5' 

 9_U. 



"~ 3 O 

 3 



We see by this table that there is a sensible increase in the 

 mean annual quantity of rain as we proceed from 1778, the time 

 when these observations began, and especially during the last 

 decade. This remark does not accord with the common notion 

 that countries covered with wood are the most rainy ; for since 

 the beginning of these observations, and especially during the 

 last 10 years, the forests have been very much destroyed, not 

 only on the territory of Viviers, but over the whole department 

 of Ardeche ; and at present there remain only a few inconsider- 

 able portions of soil covered with wood. 



The heaviest rain which 1 have observed is that of Sept. 6, 

 1801. It rained during 18 hours without interruption, and 

 there fell 13 inches 2£ lines of water. 



During these 40 years, making altogether 14609 days, there 

 have been 3921 rainy days, which, in round numbers, amounts 

 to 98 rainy days in the year. These 3921 rainy days were 

 divided among the four decades as follows : 



Decades. Rainy days. 



1778—1787 830 



1788—1797 947 



Decades. Rainy days. 



1798—1807 1062 



1808—1817 1082 



And divided among the 12 months of the year as follows : 



• On comparing the observations of the quantity of rain made at different 

 places, I think I perceive that the second maximum is greatest in countries situated 

 uear the Mediterranean, and the nrst maximum greatest in the countries situated 

 near the ocean. 



