ASTRONOMY. 251 



they were ascertained on a comparison of many years by the Royal 

 Society of London, at London are, south-west winds, one hundred and 

 twelve days ; north-east winds, fifty-eight days ; north-west winds, fifty 

 days ; west winds, fifty-three days ; south-east winds, thirty-two days ; 

 east winds, twen-ty-sixndays ; south winds, eighteen days; north winds, 

 sixteen days; making altogether three hundred and sixty-five days. 



CLOUDS 



Are masses of condensed vapour, more or less opaque, formed and 

 sustained by different agencies, at various heights in the atmosphere. 

 They are named and classified as follows: 



1. SIMPLE FORMS. 



First Cirrus, or cure clouds, consisting either of white parallel lines, 

 faintly pencilled on the azure sky, or of bending spreading fibres, starting 

 from central points in all directions, and commonly called mare's tails. 



Second Cumulus, or slacken cloud, a spreading roundish kind of- 

 cloud, full of conical lumps, increasing upwards from a horizontal base. 



Third Stratus, or fall cloud, is of a foggy, misty character, consist- 

 ing of an extended, unbroken, horizontal sheet of vapour, encreasing 

 from below. 



INTERMEDIATE FORMS. 



Fourth Cirro-cumulue, or sonder cloud, a series of small, well 

 defined, roundish masses, in close horizontal arrangement. 



Fifth Cirro-stratus, or n-ane cloud, usually horizontal masses, 

 forming a low spreading cloud, thin towards its circumference. 



3. COMPOUND FORMS. 



Sixth Cumolo-stratus , or twain cloud, round headed and moun- 

 tainous in appearance, and seem to be a combination of the cirro- 

 stratus with the cumulus. 



Seventh Cumulo-cirro-stratus, or nimbus the RAIN CLOUD, that 

 form into which the other clouds revolve previously to rain. It is an 

 horizontal sheet, above which the cirrus spreads while the cumulus 

 enters it sideways, or from beneath. 



