SCO SCIENTIFIC RECORD TOR 1884 



the cuimilns clouds by day and their sinking by nigbt ; tbe true form 

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

 the cloud where the lightning is developed. {D. M. Z., i, i). 4.) 



150. [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, 18S3, 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 

 TJ. S. Geological Survey.] 



151. A. Richter proposes to determine the altitudes of clouds and 

 their 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 

 to the Berlin Physical Society in ]March, 1881. [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- 

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

 to the condition of the atmosphere at high regions.] {Nature, xxix, 

 p. 363.) 



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

 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 geographical distribution is 

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

 at any one time; the foggiest months are January and June ; J^^ovember 

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

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

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

 striking hills and cliffs. Hitherto the observers have simjjly distin- 

 guished between mist, fog, and heavy log. Gladstone urges that the 

 record should be made more accurate, using Cunningham's proposition, 

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

 circle, and becoming invisible, requires the entry of the word "fog." 

 Symous proposes a substitute, as follows: A series of 5 screens, each 

 of black and white stripes, screen No. 5 liaving broad stripes, and No. 

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

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

 time the screens are to be illuminated l)y i huni) from behind, all being 



