130 



TRANSLATION. 



Atmospheric Micrography. Observations on the Cor- 

 puscles suspended in the Atmosphere. By M. Pouchet. 



(' Comptes rendus,' March 21st, 1859.) 



The atmosphere contains, in suspension, numerous cor- 

 puscles, consisting of the detritus of the mineral crust of the 

 earth, animal and vegetable particles, and the minutely 

 divided debris of the various articles employed in our wants. 

 These various kinds of corpuscles are more numerous and 

 more voluminous in proportion to the degree in which the 

 atmosphere is agitated by the wind ; and they constitute 

 what we term " dust/' 



This " dust" being simply the deposit of the corpuscles 

 carried in the atmosphere, it is evident that the attentive 

 study of its composition is simply a microscopic analysis of 

 the air. 



The granules of mineral origin, partly going to form the 

 dust, present but little variety. They are derived essentially 

 from the detritus of the rocks which are exposed in the 

 country where the dust is observed. 



The debris derived from the animal kingdom consists 

 chiefly of the following articles : — various animalcules in a 

 dry state and of extreme minuteness, such as entozoa be- 

 longing to the genus Oxyuris and Vibriones of several 

 species. I have often also noticed the skeletons of siliceous 

 Infusoria, especially of Naviculce, Bacilhirice, and other 

 diatoms ; fragments of the antennae of Coleoptera ; scales of 

 diurnal and nocturnal Lepidoptera j fibres of wool of various 

 colours derived from our clothes, often of a beautiful blue, 

 bright red, or green; hairs of the rabbit, bat, &c. ; the 

 barblets of feathers; fragments of the tarsi of insects; 

 epithelial cells; fragments of the skin of various insects; 

 particles of cobweb. Twice only, in more than a thousand 

 observations, have I observed one of those large ova of 

 Infusoria having a diameter of 00150 mm., denominated by 

 naturalists " cysts." 



The corpuscles contained in "dust" belonging to the vege- 

 table kingdom, observed by me, are the following: — frag- 



