28 THE METEOROLOGY OF JAMAICA 



(3) CiREO-cuMULus. This cloud consists of thin sheets of 

 small and separate flakes, arranged more or less regularly 

 along|two sets of parallel lines. When seen at great elevation, 

 the arrangement resembles the scales of mackerel ; when seen 

 lower.]; down, the large size of the lozenge-shaped flakes give 

 the sky the appearance "of a gigantic chess-board." The 

 flakes have no fibrous texture, but the parallel lines refer 

 them to cirrus ; for long cirrus stripes are often striated, or 

 cut off into small and equal lengths, and if a number of such 

 stripes were placed side by side, we would have the form 

 but not the texture of cirro-cumulus. This may be some 

 apology for the word cirro ; but there can be little or none 

 for the word cumulus, because the new cloud alto-cumulus 

 is very similar to (3), with this difference, that the com- 

 ponent parts are soft rounded masses small cumuli, in 

 fact. 



(4) Strato-cirrus. A cloud somewhat resembling cirro- 

 stratus, but thick and woolly. It is a tropical cloud, and 

 has not received much attention from the meteorologists of 

 northern latitudes. 



When rain begins to fall from a large cumulus, a quantity 

 of cloud is poured into the air from the top of the cumulus, 

 as smoke from a factory chimney. This takes place in all 

 parts of the world when rain falls from cumuli, but in the 

 temperate zones only a little cirriform cloud is thrown off. 

 In Jamaica the process is on a gigantic scale, and the cloud 

 is sjDread out as a sheet far and wide, so as to shade the land 

 for some hours from the direct rays of the afternoon sun. 

 It is therefore a common cloud in the west-central district 

 of Jamaica during the summer and autumn months. Its 

 texture at first is thick and woolly, but as it spreads the 

 sheet becomes thinner. It then settles down, often passing 

 through different forms, and finally disappears, leaving the 

 evening sky perfectly clear. 



Now, by means of a sextant, some careful observations were 

 made of the altitude of the tops of well-formed cumuli, whose 

 distances could be ascertained by their rain falling on 

 mountain ranges or by the average interval between the 

 distant thunder and lightning; and it was found that the 

 average height of such well-formed cumuli was as much as 



