THE CLOUD REaiON, ETC. 263 



yelocity of the waves in the Atlantic is 22-3 miles an hour, oiBf 

 Cape Horn 26-8.* 



508. It would aiford a pleasant and agreeable diversion for a 

 Determining tiie sQuadrou of luen-of-war, as they pursue their voyae^e 



height 'Of clouds at f- . ,-, -, ■ f • i i n • n • ^ 



sea. at sea, to amuse themselves and instruct then" triends 



at home with observations upon all such phenomena. Those who 

 are willing to undertake the clouds will have no difficulty in devis- 

 ing 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 thrcc to fivc milcs iu height ; there the height of 

 douwVincfined plane, clouds is Imow to bc 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 fi^om the equa- 

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

 which have taken place h'om 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. AVe are also 

 indebted to Piazzi Smyth for interesting observations on the cloud 

 region in the belt of north-east trades and of the upper counter 

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

 height of 12,200 feet, dming the months of August and September, 

 1856.t The cloud region of the trades was between 3000 and 

 5000 feet high ; of the upper or south-west current, it was above the 

 mountain. Islands only a few hundred feet high are generally 



* From Captain Ginns Abstract Log: — 



" Saturday, September lltli, 1858, doubling: Cape Horn, The long regular swell 

 during this part of the day afforded me another opportunity of trying the velocity 

 ■of the waves. This I did by paying out the log-line enough to be equal to 13 

 knots with tlie 14-second glass ; then by watching the chip— to which I had fixed 

 ii piece of white rag to render it more distinguishable — as it appeared on the crest 

 of a well-defined wave, and turning the glass at the same time, and then noting 

 where the crest of a wave is at the moment the glass is ' out.' 



" I have several times before tried the experiment in tliis way with the same 

 length of line out astern, and have always found about the same rate for the 

 velocity, namely, 22 to 23 miles an hour ; but to-day I found it to be considerably 

 more, namely, 26 to 28 miles an hour. Tims the crest of a wave would pass, while 

 the ll-second glass ran out, from the ])lace wliere the log-chip was towing astern 

 (13 knots) to just ahead of the ship. The length of the sliip is equal to about 6J 

 knots : the ship's speed at the time was 8 knots; thus, 134-GJ-t-8 = 27|-. A few 

 days ago I tried the same experiment, and found the velocity to be 22 to 23. 

 What has accelerated the velocity of these waves ? Has the soundings anything to 

 <io with it ?" 



t Teneriffe. An Astronomer's Experiment. London, 1858. 



