440 SCIENTIFIC RECORD FOR 1852. 



fog-drops, such as optical theories show cannot j)OSsibly produce rain- 

 bows. {Nature, xxv, p. 527.) 



To this Fonvielle replies that when Kratzensteiu, in 1744, advocated 

 Halle's ojjiuion with regard to the vesicular state of the particles of fogs 

 and clouds as demonstrated by the absence of rainbows, he was misled 

 as subsequent observers have been by the fact that the intensity of re- 

 flected light is not sufQcient to show the rainbow, and he quotes an 

 observation by Faye, in 1S49, to the eflect that an electric or other bright 

 light thrown upon a natural or artificial cloud will prove a convenient 

 method of investigating this subject. {Nature, xxv, p. 529.) 



In 1872 the present writer sketched out the simjjle details of a plan 

 for observing the heightsof clouds at night time; it consisted essentially 

 in throwing a well-defined beam of electric or calcium light vertically 

 ujiward and observing from a neighboring station the apparent altitude 

 of the bright spot visible on the under side of the cloud. 



To the preceding, Dr. Kopp says, " There may be difficulties in the 

 way of deciding, by direct observation, as to the form of the cloud- 

 particles when their globules are crystals, but since de Saussure and 

 Waller both record the results of microscopic observations it seems 

 ])ossible to carry such investigations still further. {Nature, xxv, p. 31.) 



The questions at issue between Fonvielle and Kopp have been inves- 

 tigated by Eloy, ayoung aeronaut, who, after having made an interesting 

 balloon ascent on the 7th of May, 1882, at Paris, has proposed a series of 

 ascents from La Villette gas works, Paris, in order to make special ob- 

 servations on the nature, formation, dimensions, movements, and loca- 

 tion of clouds. In the ascent of May 7, starting at midday, he reached 

 an altitude of 1,900 meters, where the temperature was higher than at 

 1,400 meters. He found a southeast current up to 300 meters, and also 

 again above 1,400 meters, but a northeast current in the interior. 

 {Nature, xxvi, pp. 67 and 72.) 



His subsequent ascent, of May 18th, was made on the eleventh day 

 of a well-defined period, during which the prevailing wind was almost 

 without intermission a strong northeasterly breeze which had been 

 detrimental to agriculture. The sky was clear, deep blue, and the air 

 cold and dry. A large number of dense, small cumuli, dark, well defined, 

 with round edges, were seen carried by with the wind almost without 

 intermission, except during the eclipse, when the weather was magnifi- 

 cent. This period having terminated only on the 20th, by a total 

 change of wind, the observations taken may be considered as giving 

 a fair idea of the atmospheric conditions which prevailed during so 

 many days. These clouds were floating at an altitude of more than 2,000 

 meters, and very cold, the thermometer having descended abruptly to 

 4° and G"^ centigrade. When crossing this cloud, the aerial travelers 

 perceived no isolated flakes of snow, but the air seemed illuminated by 

 sudden lights, as if rays traveling from the sun had been reflected by 

 jninute icy particles. The balloon having ascended to the upi^er surface 



