* 658 



«.— CLASSIFICATION OF THE CLOUDS. 



Since the discovery of Buys-Ballot's Law (page 113), and of the Cyclonic 

 and Anti-cyclonic Gales of extra-Tropical latitudes, the study of the 

 Clouds has assumed a new importance, as showing the movements of the 

 air in the upper atmosphere, but, in the first place, it requires a practiced 

 eye for Cloud observations, and this no person has a better chance of 

 acquiring than the seaman. There is at present not enough known of 

 the subject to lay down any very reliable rules, and there is great practical 

 difficulty even in drawing up a system of nomenclature, which can be 

 universally adopted. Many capable observers are now actively engaged 

 in the study of this subject, and we cannot afford space here even to 

 give a list of the works written by them. Many valuable Papers, well 

 illustrated, are to be found in recent " Journals of the Meteorological 

 Society," especially that for 1887, to which the student is referred for 

 full particulars.* 



On pages 200 — 203 we have previously given some particulars, 

 illustrated with a diagram, of the distribution of Clouds within the areas 

 of Cyclonic Storms passing over the British Isles, mainly due to the 

 Rev. W. Clement Ley, M.A., F.M.S., who has devoted many years to the 

 study of this subject. A remarkable feature is the direction taken by the 

 higher Clouds in these storm areas ; with the wind in one of these storms 

 blowing on the observer's back, the Clouds high in the atmosphere 

 indicate that the direction of the wind is from left to right of the observer, 

 which would seem to show a rising of the wind in a spiral form. 



" The researches of Mohn, Hildebrandsson, Buchan, Ley, and others, 

 seem to prove that in all cases which they have investigated by means of 

 wind direction and the motion of Cirrus clouds, the air flows spirally into 

 an area of low pressure at the surface of the earth, and to some extent 

 out from it in the upper regions of the air ; whilst the order is reversed 

 with areas of high pressure, the lower air flowing out from, and the upper 

 air in towards, their centres. It remains to be proved whether the same 

 law holds good with regard to the area of high pressure in the centre of 



the Atlantic It must be remembered that there are upper 



currents of air which (owing to the absence of moisture) do not carry 

 Clouds along with them, and that they need some other means than 

 Cloud motion to detect them." — Captain Henry Toynbee. 



Mr. Ley, and numerous other meteorologists, also consider that the 

 classification of the late Mr. Luke Howard, which has been in use for the 

 greater part of this century, is not suitable for the present state of 

 weather knowledge. Without materially altering the old nomenclature, 

 they are of opinion that the Clouds may be divided into Upper and Lower 

 Clouds, or those high in the atmosphere, such as Cirrus, Cirro-cumulus 

 and Cirro-stratus, and those nearer the earth's surface, including Stratus, 



* Sw, also, " Modern Developments of Cloud Knowledge," by the Hon. R. Ab>3r> 

 ^j«omby, in the " Journal of the Scottish Meteorological Society," 1839, pages S- IS, 



