ATMOSPHERIC MICROGRAPHY. 167 



modification of that employed by Dr. Maddox, the whole 

 turning freely, so as to present its orifice constantly to the 

 wind, the particles impinging on a vertical slip of microscopic 

 glass painted with glycerine, and capable of being transferred 

 without danger of their being rubbed off, to the table of the 

 microscope, care being taken that everything was made pre- 

 viously as clean as possible. 



In the Presidency jail the apparatus was placed within the 

 largest enclosure, on an open space of grass, to the east of a 

 large tank in which the native prisoners bathe. The most 

 convenient locality at Alipore was to the north of the hospital- 

 tank, between the compound of the jail and the tidal nullah, 

 from which it was separated by the wall of the enclosure. 

 The diaphragm Avas removed every twenty-four hours. The 

 magnifying power was in general 400 diameters, but higher 

 powers, ranging from 800 to 1000 diameters, were used for 

 more minute bodies. Dust from shelves of iron or stone was 

 purposely excluded, as algae or other bodies might have grown 

 up from particles conveyed from the soil, rather than from the 

 atmosphere. The mouth of the apparatus was about five feet 

 from the ground. 



On microscopic examination the deposits were found to 

 consist of various matters. 



1. Particles of silicious matter. 



2. Particles of carbonaceous matter. 



3. PVagments of hair and other animal substances. 



4. Fragments of cellular tissue of plants. 



5. Pollen grains, amongst which those of several common 

 grasses could be easily recognised,' and a few belonging to 



ing of June, and more or less wet to the beginning of September, wbicli 

 accords witb the dates appended to the figures. 



' This may be of importance after the very interesting observations of 

 Mr. Biackley on the connection between the pollen grains of grasses and 

 liay asthma. [A brief record may be given here of Mr. Blackley's 

 results. They were commenced in April, and continued till the end of 

 July. In one series the air of a meadow at the average breathing level, 

 4 feet 9 inches from the ground, was examined. A slip of glass, coaled 

 with a thin layer of a non-drying liquid, was exposed horizontally. 'J'he 

 daily results are tabulated. The highest number of pollen grains obtained 

 on a surface of a square centimetre in twenty-four hours was 880 on June 28. 

 Sudden diminutions in the quantity of pollen — when these occurred in the 

 asce'nding scale between May 28 and June 28 — were invariably due to a 

 fall of rain, or to this and a fall in the temperature combined. The amount 

 of pollen in the higher strata of the atmosphere was examined by means of a 

 kite, which by being attached to other kites sometimes attained an elevation 

 of 1000 feet. Pollen was found to be much more largely present at the 

 upper levels than at the " breathing level," in the proportion, in fact, of 19 to 

 1. Abuudaut proof was also obtained of the presence of fungoid spores in 



