!B00 SCIENTIFIC RECORD TOR 1884 



the cumnlus clOl^ls by day and their sinkiug by night ; the true form 

 of the thunder clouds and their method of growth, and the locus within 

 the cloud w^here the lightning is developed. {B. AL Z.. i, p. 4.) 



150. I It seems strange that the numerous suggestions- made in Eng- 

 land, Germany, and America for many years past as to the use of pho- 

 , tography for determining the height of clouds should as yet have been 

 ' earnestly taken up by only one person, Mr. W. Abney, who, in Septem- 

 ber, 1883, began active work on this subject at Kew. A beginning in 

 ' this direction was made in 1871 by the Signal Office, and we are now 

 promised that good work will be done by the photographers of the 

 ^U. S. Geological Survey.] 



A51. A. Richter j^roposes to determine the altitudes of clouds and 



'fChcar true velocity from observations made by two observers at quite a 



-distance apart vertically instead of horizontally. This method is espe- 



^cially applicable to mountain regions and to those who have access to 



very tall towers. (D. M. Z., i, p. 166.) 



152. Various forms of sound radiometers were described by Dworak 

 tto the Berlin Physical Society in March, 1884. [Either by these or by 

 ; means of Edison's phonautograph we may still hope to obtain some 

 ; method of measurement of the intensity of thunder. The gradual dying 

 ; away of thunder and of the rolling noise frequently likened to an explo- 

 fsiou emanating from a bright meteor can give us some information as 

 tto the condition of the atmosphere at high regions,] {Natut^e, xxix, 

 p.. 363.) 



153. J, H. Gladstone, as a member of the Commission for Light- ETouses 

 and Marine Signals, has expressed the necessity and possibility of estab- 

 lishing some standard for the measurement of the density of fog. His 

 observations show that only spots or streaks of (country are covered at 

 any one time with dense fog; that the fog is much more uniform over 

 the sea than over the land, and that its geograpliical distribution is 

 very irregular. 'Usually only a small portion of Great Britain is affected 

 at any one time; the foggiest months are January and June ; November 

 is the foggy month for London, but not so for the rest of England. The 

 foggiest portion of the coast is the southern ])oint of the Hebrides, and 



; fog especially occurs where the wind from the sea is turned upwards by 

 ;sii'iking hills and cliffs. Hitherto the observers have simi)ly distin- 

 • giius.hed between mist, fog, and heavy log. Gladstone urges that the 

 ireotjffld should be made more accurate, using Cunningham's pro})Osition, 

 inameV : a staff placed at 100 yards distance in front of a painted red 

 (Circle, ;afud becoming invisible, requires the entry of the word "fog." 

 ^ymons ;j>i:oposes a substitute, as follows: A series of 5 screens, each 

 oif black and white stripes, screen No. 5 having broad stripes, and No. 

 Imacrow ones. The fogs to be recorded as of intensity from 1 to 5 

 actixoiErting to the visibility or invisibility of these screens. At night- 

 time t!lheasej^£us are to be illuminated by i lamp from behind, all being 



