24 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



CLIMATE OF PERU. 



Dr. Miihry remarks of the coast of Peru that it presents 

 one of the most interesting excej:>tions to the general system 

 of terrestrial meteoration, and, as is usually the case in the 

 science of meteorology, that the true explanation of the anom- 

 aly is only an additional proof of the soundness of the general 

 laws as established. In the course of his article he remarks 

 that the narrow strip of country, only about fifteen geograph- 

 ical miles in width, lacks the trade wind, rain, and thunder- 

 storms, and is, consequently, a desert, although it is yet very 

 fertile where water is found ; and the air is not destitute of 

 moisture, having, indeed, no slight degree of saturation. The 

 temperature is by several degrees too cold for its latitude, 

 and the air is characterized by continued damp fogs, the so- 

 called garuas. The reason of this variation from the usual 

 system he finds in the fact that the trade wind blowing from 

 the Andes comes down beyond the coast, which, consequent- 

 ly, is in the lee or the shadow of the wind; and, in addition 

 to this, there is a powerful cold ocean current flowing past 

 it. The trade wind thus does not reach the lower strata of 

 the atmosphere until it gets some considerable distance out 

 to sea, and it is at this point that the rains first manifest 

 themselves. The fog referred to is thought to be due un- 

 doubtedly to the cold antarctic current, so that, if the one 

 were not present the other would immediately disappear. 

 17 C.March, 1871,112. 



FORMATION OF CLOUDS. 



An English writer, while criticising somewhat unfavorably 

 Professor Poey's new classification of clouds, remarks that in 

 his opinion there are but three ways in which it is possible for 

 clouds to be formed. These are, first, the cooling of a mass 

 of air in situ by radiation ; this forms stratus. Second, the 

 cooling of a mass of air by diminished pressure when it flows 

 in an ascending column; this forms cumulus. A modification 

 of the process is when sudden expansion takes place above, 

 so as to diminish the pressure through the entire height of 

 the column of air, and, in consequence of the cold due to 

 the diminution of pressure, produces condensation of vapor 

 throughout the column. This is Espy's explanation of water- 



