14 



MR. BIRT'S ARRANGEMENT OF CLOUDS. 



DURING a series of meteorological observations, in which I have 

 been engaged for some years past, I found it important to register the 

 appearance of the clouds, and for this purpose directed considerable 

 attention to them. When I first registered them, I adopted the nomen- 

 clature of Howard, but soon found it insufficient to convey to my mind, 

 after a lapse of time, a clear and distinct idea of the clouds I had seen 

 at the time of registering. I was, therefore, under the necessity of 

 sketching out a nomenclature for my private use ; when, after a course 

 of daily observations for upwards of twelve months, I found so many 

 distinct varieties and modifications, not mentioned by Howard, that I 

 was induced to collect and classify them for the benefit of meteorolo- 

 gists, generally ; and with this view I have laid them before the Eclec- 

 tic Society of London. 



The clouds, I conceive, may be divided into three distinct divisions 

 or classes, according to their structure, as all those that I have hitherto 

 observed may be referred to one of them. There are clouds which 

 possess a structure similar to those known by the familiar name of fogs 

 or mists, and these are observed in the upper and lower regions of the 

 atmosphere : for this class I conceive the most appropriate name to be 

 Nebula ; and I have noticed five distinct varieties and modifications, 

 two in the upper, and three in the lower regions. The terms I have 

 applied to those observed in the upper region, founded on their appear- 

 ance, are Nebula expansus, and N. siriatus ; or an expanded nebulosity, 

 and a streaked nebulosity. The term applied to those observed in the 

 lower region is N. stratus, as expressing that it is spread over a por- 

 tion of the earth's surface. 



The next class is more extensive, and includes all those clouds that 

 possess a fibrous structure ; the term Fibrus, employed generically, will, 

 I conceive, sufficiently point out the structure of the cloud to which it 

 is applied. The varieties which compose this class I have arranged 

 according to their appearance and relative altitude, commencing with 

 the long, thread-like fibres, which, on close inspection, I have found 

 on some occasions to result from a resolution of the nebulosity of N. 

 striatus ; this variety I have termed Fibrus Jiltformis. These clouds 

 sometimes unite and form broad bands, stretching from one part of the 

 horizon to another : to express this appearance, I have suggested the 

 term F. striatus. On some occasions these bands unite, and form- 



* The paper, of which the present article is an outline, was read before the 

 Eclectic Society of London, on November 26, 1833. 



