20 OP CLOUDS. CHAP. l.7. 



of rain and tempestuous weather ; and modern 

 meteorologists have corroborated the speculative 

 notions of the ancients, and have observed the 

 prevalence of the wanecloud to be usually 

 followed by bad weather, as will be further 

 discussed when I come to speak of prognostics 

 of atmospheric changes. 



SECTION VII. 



Of the Cumnlostratus or Twaincloud PI. III. 

 Fig. 1. 



CYMVLOSTRATVS. Def. NVBES DENSA IRREGVLARIS 



BASIN PLANAM VNDIQUE SVPERCRESCENS. 



THE change of the cumulus into the ciimu- 

 lostratus is effected in the following manner: 

 the cumulus, losing its hemispherical figure, 

 increases irregularly upward, grows more dense, 



Lucidus orbis erit, frustra terrebere nimbis 

 Et claro sylvas cernes aquilone moveri. 



Virg. Geor. lib. i. 460. 



The radii diversi xe erumpciitcs are probably the same as 

 the ca*$ii, described by Aristotle, in his Meteorologica. 



