446 METEOROLOGY. 



tivcly glacial, an effect probably due to the uearuess and the qaantity 

 of snow wliich compose this type of cloud. 



The cirrus being much more elevated and the cirro-stratus much less 

 abundant, although both formed of glacial aiglets, have not the same 

 influence on terrestrial temperature. According to Howard, the cirro- 

 cumulus is formed from a cirrus, or a number of small separate cirrus 

 by the fibers collapsing, as it were, and passing into small, roundish 

 masses, in which the texture of the cirrus is no longer discernible, 

 although they still retain somewhat of their relative arrangement. Tliis 

 change takes place either throughout the whole mass at once, or i^ro- 

 gressively from one extremity to tlie other. In either case the same 

 effect is produced on a number of adjacent cirri at the same time and 

 in the same order. It ai^pears in some instances to be accelerated by 

 the approach of other clouds. . This modification forms a very beautiful 

 sky, sometimes exhibiting numerous distinct beds of these small con- 

 nected clouds, floating at different altitudes. The cirro-cumulus is 

 frequently seen in summer, and is attendant on warm and dry weather. 

 It is also occasionally and more sparingly seen in the intervals of showers 

 and in winter. It may either evaporate or pass to the cirrus or cirro- 

 straiiis. 



IV. — Pallium, (PoiiY,) (vel nimMs, Howard.) 



Under the generic name of pallium I have classed two forms of cloud, 

 which i)resent the appearance of a mantle or veil of considerable extent, 

 of very compact texture, well defined at the edges, of excessively slow^ 

 motion, and embracing the visible vault of the sky. As the pallium is 

 formed of cirrus or of cumulus, it is distinguished into pallio-cirrus autl 

 pallio-cumulus. The appearance of this cloud signalizes bad weather, 

 and its disappearance, good weather. 



The stratum of pallio-cirrus is first produced, and some hours or days 

 afterward that of pallio-cumulus is formed under it. These two strata 

 remain in view at a certain distance from each other, and in their recip- 

 rocal action and reaction are accompanied with storms and heavy rains, 

 and with considerable electric discharges. They are both electrified, 

 but with contrary signs ; the superior stratum of cirrus is negative, and 

 the inferior one of cumulus is positive, the same as the rain v>'hich is 

 disengaged, while the electricity of the air, at the surlace of the earth, 

 is negative. But when these two strata attract each other a discharge 

 is produced, and the inferior stratum continues to pour out the surplus 

 water it contained, without giving any sign of electricity, more than the 

 air in contact with the earth. This state continues until the inferior 

 stratum opens, afterward the superior, and then disappear, one after 

 the other, fine weather succeeding. The pallium chiefly predominates 

 during the rainy season, in tropical regions, and in the higher latitudes 

 during winter, at the time of falls of suo\t. A part of the pallio-cumulus, 

 which has not been reduced, or has not been scattered to other regions, 

 gathers at the horizon, and is transformed into the cumulus. As to the 



