44 Meteorological Observations. 



tration, nor am I able even to suggest a reason for it. It 

 appears to depend neither on the dampness nor dryness of 

 the air, the clearness or cloudiness of the sky, the temper- 

 ature, the prevailing winds, nor the height of the baro- 

 meter. 



Generally speaking, when the air is saturated with mois- 

 ture it is then clearest, but I have seen the air also beautiful- 

 ly clear, when the dew point was ten or twelve degrees of 

 Farhenheit below the temperature, and also perfectly hazy 

 during damp weather. 



Dr. Prout in his Bridgwater treatise has given it as his 

 opinion that the slight excess of oxygen which the air con- 

 tains above the proportions of oxygen and nitrogen required 

 to form a chemical compound, may at times enter into che- 

 mical composition with the vapour of water contained in the 

 air, and thus produce a change in its hygromatic state. I do 

 not find that Dr. Prout has stated his reasons for consider- 

 ing this hypothesis as probable, but as coming from such an 

 authority it must be considered at least as possible, and then 

 may not perhaps this chemical change produce the haziness 

 in question? 



Your remarks on mists and fogs are corroborated by my 

 observations, the detailed results of which will be published 

 at some future time. 



carried in the atmosphere by land winds, so as to affect its trans- 

 parency. In the south of Italy the wind described by Schouw in our 

 present number must carry the earthy particles with which it darkens 

 the air at certain seasons across the Mediterranean from Africa, a dis- 

 tance of from 400 to 600 miles. The earthy particles with which the 

 westerly winds are loaded in Kemaon in April and May, must be carried 

 a distance of from two to three hundred miles, and in the latter por- 

 tion of their course for 150 miles over damp wooded tracts and moun- 

 tain ridges of from 6,000 to 8,000 feet in height, before they are depo- 

 sited at night during the subsidence of the wind from local causes. — Ed. 

 Cal. Journ. Nat. Hist. 



