PE0GEE8S OF METEOROLOGY IN 1889. 237 



its path is contimuilly varying. The outline of the object has a tremu- 

 lous motion, and so becomes ill detiued. At the same time retlectiou 

 occurs where there is refractiou at the surfaces of separation of hetero- 

 geneous portions, and the reflected light is diffused as a general glare. 

 The combination of the quivering of outline and the loss of direct light, 

 as a dilfused glare, may possibly give the appearance called haze which 

 is seen in the middle of a hot, cloudless, summer day. The author 

 mentions other cases of haze which may possibly be likewise due lo op- 

 tical heterogeneity. {Nature, xxxix, p. 323.) 



In a series of letters to Nature by a number of prominent scientists, 

 a valuable contribution has been made to our knowledge of the peculiar 

 characteristics of different types of haze. Professor Tyndall opened 

 the subject by reporting his observations of the prevalence in the val- 

 leys of the Alps of a fine haze appearing as long horizontal striae 

 Amid the haze were often patches of cloud which disappeared under the 

 sun's rays, leaving the permanent haze behind. From this fact he is 

 certain the haze is not aqueous, and suggests that it may be due to 

 autumn pollen in the air. 



Mr. Johnston-Lavis corroborates the observation that haze assumes 

 the form of horizontal strata, and supports the theory of its micro- 

 organic nature. During the hottest and driest weather of summer, 

 haze similar to that observed by Professor Tyndall in the Alps can be 

 seen in the Gulf of israi)les and other parts of the Mediterranean coasts 

 at an average altituae of 1,500 feet and rarely reaching 2,000 feet. 



M. d'Abbadie furnishes a valuable list of special names by which 

 such haze is designated in many warm countries, where it is most fre- 

 quently observed. In Ethiopia, where it is called qobar, this haze is of 

 extraordinary density and hides all the features of the landscape be- 

 yond the distance of a mile, and conceals stars of the third magnitude 

 even in the zenith. Observations of its occurrence are quoted from 

 Peru, Hayti, Switzerland, Spain, and other localities; its color is a light 

 butt, and when dense, a "lurid gray, verging to blackness." 



W. Clement Ley reports that the horizontal layers of haze may be 

 frequently seen throughout the British Isles at times when the atmos- 

 l>here at the earth's surface is nearly calm and moderately dry. He 

 has given it the specific name of dust-haze, and distinguishes it from 

 the ordinary water haze by its color ; dust-haze ai)pears of a reddish 

 buff" tint, while water haze usually appears gray or blue in reflected 

 light, and yellow, orange, or red in transmitted light. 



ClassifimtUm of clouds. — Prof. H. H. Hildebrausson has submitted to 

 the Meteorological Congress at Paris (September, 1889) a report on 

 the classification of clouds, adopted by Mr. Abercromby and himself, 

 and urges its general adoption. This classification distinguishes ten 

 forms, as follows : 



1. Cirrus. 2. Cirro-stratns, a thin cloud veil composed of thickly 

 compacted cirrus fibres, indicative of raiUi >3, Cirro-cumulus, small 



