68 STUDIES IN THE FIELD AND FOREST. 



in order oil each side of a darker line that passes be 

 tween them, will slowly gather themselves into little 

 rounded heaps, resembling the spots on the back of a 

 fish. It is this spotted appearance which has caused it 

 to be named mackerel cloud, by the fishermen. The 

 cirrus is soon entirely resolved into this mottled cloud, 

 as if all its filaments had, by some mechanical process, 

 been twisted into rolls; but it is only by observing the 

 succeeding phenomena that we can decide whether this 

 appearance is to be regarded as the precursor of wet 

 weather. Underneath this dappled cloud there is often 

 a mass of fleecy vapor that appears to be. slowly resolv 

 ing itself into the cloud above it. As this vapor is pre 

 cipitated from the lower atmosphere, it is attracted by 

 the cloud above it which is constantly thickening as the 

 last is slowly incorporated with it. When we observe 

 this double layer of cloud, we are reassured that the 

 promises of rain held out by the former appearances, 

 are likely to be fulfilled. The upper cloud is rendered 

 more and more dense by reinforcements from this lower 

 formation, until it assumes the character of huge masses 

 rolled together in uniform heaps, which are now dis 

 tinctly tfeen moving in the direction of the wind. Rain 

 soon follows, especially if underneath all this moving 

 mass, a scud is seen proceeding rapidly in a contrary 

 direction. 



If this mackerel cloud (cirro-cumulus) happens to be 

 formed during a period of extensive drought, it is soon 

 absorbed into the upper regions of the atmosphere, and 

 the skies become clear again, without the promised rain. 

 This dissolution commonly takes place just after sunset, 

 commencing at early dew-fall. The clouds are first 

 formed from the condensation of moisture into a visible 

 shape by the cooling influence x>f contact with an upper, 



