THE NATUEAL HISTORY OF CLOUM. 4$ 



doubtful, and regard is to be had to that which ultimately 

 pfevails. 



Again, there is a transient appearance of the cirro-stratag, 

 which often accompanies the production of dew in the even- 

 ing, und denotes an atmosphere but li^^htly surcharged with 

 vapour. Not so when it appears earlier in theday, or at sun-rise 

 (according to the preceding quotation), and attended with 

 the rudiments of the cumulus. In genera], the weather 

 may be suspected of a strong tendency to wind and rain, as 

 •ften as the sky is both hazy, and deformed with numerous 

 email patches of cloud, in which the extenuated character 

 predominates; and these appeevances, together with an 

 abundance of eirro-cnmulus, indicate thunder. Before 

 storms of wind, there is in particular a feature of cirro- 

 stratus, often very slightly expressed, and in one quarter 

 only, which resenjblts the architectural c} ma. 



But the mo»t formidable appearance of the cirro-stratus 

 is that of extensive sheets, descending from the highest re- 

 gions of the atmosphere, and scarcely discernible for a time, 

 but by the prismatic colours which they assume in the vi- 

 cinity of the sun's or moon's place. These are the skreens 

 «i which are described tlK' immense circles of haloes, form- Haloes, pa^ 

 isig, by their occat;ionai intersections, parhelia, and parase- ''^» ^'^' 

 I^nia, rpock *ans a.ud jjaoons, which sometimes vie in splen- 

 dowT with the lumiuarjes thejtnselves. It is easy for those 

 who are acquainted with the principles cf optics, to conceive 

 how these intersecting circles are produced by light passing 

 th«oug»h sheets of cloud placed at different heights and an- 

 gles. 



iJoasist'ifnt with this is the prognostic of foul weather com- 

 tppixly deduced from the appearance of the halo. After a 

 splar lialo in spring, ,or the early part of summer, a series of 

 wet wjd cold weather umy be expected, although it should 

 iMWt cooiim-euce for some days ; during which, nevertheless, 

 the same staie of the atmosphere suiysists, as is often mani,- 

 ffistiVom the rejjet tion of the halo. Those which surround 

 tbe-EDooarkn clear nights indicate rain or snow, according 

 to the aeason of tiie year. 



In HK)untainou8 and even hilly countries, the cirro-«tratus 

 is fiCtqufttitly iieeja adhecipg t,o the more elevated points of 



land. 



