ON PHOTOGRAPHS OF METEOEOLOGICAL PHENOMENA. 141 



organisation of so novel a type of institution has left little opportunity 

 for carrying on the work of the Committee. 



Having been thus obliged to postpone much of the work they hoped 

 to carry out, they have not drawn last year's grant. 



Nevertheless, considerable progress has been made. The number of 

 persons who have sent in their names as willing to contribute has been 

 added to, the photographs in your Committee's collection have in- 

 creased from 861 to 467, and the objects of the Committee have again 

 been brought before some of the most important photographic societies. 



The result is that the secretary is continually receiving letters asking 

 for directions for the photography of clouds, for the loan of lantern slides, 

 and general instruction, the furnishing of which your Committee consider 

 by no means the least useful part of their functions. 



A fairly exhaustive trial has been made of the comparative merits of 

 the Sandell plates, and slow plates of the photomechanical type ; from 

 which it appears that the double film does not possess for cloud photo- 

 graphy any advantage over the older type of plate. Since also the 

 management of the latter after exposui-e is the easier, your Committee 

 adhere to the decision given last year, that the black glass mirror and 

 slow plate really provide the easiest means of securing good cloud 

 pictures. 



Attention must be drawn to the excellent pictures of clouds on the 

 High Alps which have been received from Mr. Greenwood Pim, who has 

 expressed his willingness to turn his attention to the photography of 

 high clouds. 



With regard to cload photographs generally, your Committee feel 

 that their collection already includes suflBciently good examples of all 

 the commoner varieties of cloud which are capable of being so repre- 

 sented, and therefore think that there is no scientific object to be served 

 in simply multiplying prints. Consequently, during the past year they 

 have not sought such contributions, but in soliciting aid have invited 

 observers to study especially the changes of high-level clouds. This is 

 a work of considerable difficulty, and there are probably few persons who 

 possess at once the requisite skill and sufficient leisure. 



The records of cloud forms may thus be said to have been secured, 

 and the next question is, How may they be utilised ' for the elucidation 

 of meteorological phenomena ' ? 



Upon what problems do they bear ? This is easily answered. They 

 should give first the means of settling precisely what connection there 

 is between particular cloud forms and other atmospheric conditions, 

 and in the next place they should give a clue to the explanation of their 

 own forms. 



In order to attack the first problem the great want is an efficient 

 cloud atlas of the higher clouds, such as was undertaken some time ago by 

 the International Committee. This atlas has not yet been published, and 

 in it, moreover, it is proposed to arrange clouds under the names suggested 

 by Messrs. Hildebrandsson and Abercromby, a system which English 

 meteorologists have not yet adopted. Indeed, as your Committee have 

 observed in a previous Report, the system of nomenclature should follow 

 and not precede the study of the two problems stated. 



The varieties of the lower clouds are pretty well understood ; it is 

 with the higher clouds that all difficulties arise. Your Committee there- 

 fore suggest that they should be empowered to arrange for the publica- 



