§509. THE CLOUD REGION, ETC. 273 



Detei-mining the sQuadron of men-of-war, as tliey pursue their vov- 



height of clouds at -^ i i i • ■, ■ 



sea. age at sea, to amuse themselves and instruct their 



friends at home with observations upon all such phenomena. 

 Those who are willing to undertake the clouds will have no diffi- 

 culty in devising a plan both for the upper and the lower strata. 

 509. Over the land the cloud region is thought to vary from 

 Cloud region at sea in thrcc to fivc milcs in height; there the height of 



the shape of a double ii-i i -ita •• 



inclined plane. clouds IS Kuown to DC vcry Variable. At sea it IS no 



doubt less so. Here the cloud region is somewhat in the form of 

 a double inclined plane, stretching north and south from the equa- 

 torial cloud-ring as a sort of ridge-pole. In the balloon ascents 

 which have taken place from the Kew Observatory in England, 

 it has been ascertained that there the cloud region is from 2000 to 

 6500 feet high, with a thickness varying from 2000 to 3000 feet, 

 and that its temperature at the top is not lower than it is at the 

 bottom of the cloud, notwithstanding its thickness. We are also 

 indebted to Piazzi Smyth for interesting observations on the cloud 

 region in the belt of northeast trades and of the upper counter 

 current there. They were made from the Peak of Teneriffe, at the 

 height of 12,200 feet, during the months of August and Septem- 

 ber, 1856.* The cloud region of the trades was between 3000 and 

 5000 feet high ; of the upper or southwest current, it was above 

 the mountain. Islands only a few hundred feet high are gener- 

 ally cloud-capped in the trade-wind regions at sea ; another indi- 

 cation that, with a given amount of moisture in the wind, the cloud 

 region is higher at sea than it is over the land. For most of the 

 time during his sojourn on the Peak, the sea was concealed from 

 view by the cloud stratum below, though the sky was clear over- 

 head. Farther to the north, in the Atlantic, however, as in the 

 fog region about the meeting of the cool and warm currents near 

 the Grand Banks, the look-out at the masthead often finds him- 

 self above the fog or cloud in which the lower parts of the ship 

 are enveloped. Going still farther toward the north and reaching 

 the ice, the cloud region would again, for obvious reasons, mount 

 up until you reached the open sea there, when again it would 

 touch the earth with its smoke. 



same experiment, and found the velocity to be 22 to 23. What has accelerated the 

 velocity of these waves? Has the soundings any thing to do with it?" 

 * Teneriffe. An Astronomer's Experiment. London, 1858. 



s 



