522 



is now added, from Calcutta, a memoir by Dr. Cunningham on 

 "Microscopic Examinations of Air," which derives importance 

 not less from the moderate and unprejudiced tone of the author 

 than from his evident familiarity with the minute organisms in- 

 volved in the investigations. In looking for some perceptible 

 connection between the prevalence of certain forms of disease and 

 the occurrence of any particular bodies in the air, the dust accumu- 

 lated on shelves, etc., was avoided as too liable to error, and the 

 solid particles were collected directly from the air by a modification 

 of Dr. Maddox' apparatus, a glass slip painted with glycerine be- 

 ing arranged five feet above the ground in such a manner that the 

 painted surface should be exposed vertically to a stream of air. 

 Some sixty observations were made between February ami Sep- 

 tember, l.s 72, including both dry and rainy seasons; and powers 

 of from 400 to 1,000 were generally used. The following syn< .pais 

 of microscopic deposits found is condensed from Rev. M. J. Berk- 

 ley's review in the Quart. Jour. Mic. Science. 



1. Particles of silicious matter. 



2. Particles of carbonaceous matter. 



3. Fragments of hair and other animal substances. 



4. Fragments of cellular tissue of plants. 



5. Pollen grains ; of several common grasses, and a few of other 

 plants. No seeds positively recognized. 



6. Algse, few; but besides " those lower genera which appear 

 to be the early stages of lichens" (!) there were fragments of 

 Oscillatorise, Desmidiaceoe, Closterium, and possibly Diatomacere. 



7. Sporidia of lichens ; frequent. 



8. Spores or sporidia of fungi. These are by far the most 

 abundant bodies; which is more remarkable by contrast with 

 Ehrenberg's observations on the dust of the trade winds. Many of 

 the fungoid organisms are easily referred to faniiliar genera, Mac- 

 rosporium, Claclosporium, Sporidesmium, Puccinia, etc. Much 

 the most common are sporidia of Spheriaceos frequently in a state 

 of germination, both in dry and hot seasons. True Torula3 do not 

 appear to be present, but the yeast fungus, which after proof that 

 it is nothing more than a condition of certain species of Penicil- 



Probably several of the bodies are spores of Myxogastrsi, the 

 Amsebaj which appear in certain specimens of pure rain water being 



