1893.] 



MICKOSCOPICAL JOURNAL. 



73 



"' The coarse-grained, dark-colored dust which drifts, as all 

 Calcutta residents are aware, into the leeward corners of our 

 flat house-tops is found to contain, mixed with dried portions of 

 organic matter, certain magnetic and hyaline granules which 

 present appearances higlily indicative of previous fusion. These 

 appear mostly as opaque or translucent spheroidal bodies, some- 

 times single and isolated, and sometimes composed of more than 

 one spherule fused together, varying in size from Wu^th to aioth 

 of an inch in diameter. The opaque bodies vary in color from 

 black to rusty red, whilst the transparent spheres, by transmitted 

 light, are light-brown or yellowish, like colored glass. They 



Explanation of Figures. 



1. Opaque, sliot-like granule, 



2. Spherule including a dark crystalline 

 mass, bubbles, and a protruding opaque mass. 



3. Hyaline spherule containing crystals. 



4. Dark mass with a hyaline body in- 

 cluding bubbles. 



5. Small hyaline spherule. 



6. A composite opaque and hyaline grain 

 with bubbles and crystals. 



frequently include bubbles, patches of granular matter, and, more 

 rarely, crystals. The surfaces are usually smooth, and occasion- 

 ally bubble-like protuberances bulge out the sides. Composite 

 grains are not uncommon in which a glassy mass protrudes from 

 an opaque body. Particles presenting these characters have been 

 obtained from house-tops widely separated from one another and 

 at considerable heights, as on the tower of the High Court — facts 

 which are of importance in considering any conclusions as to the 

 origin of this material." 



One member was of opinion that they might have originated 

 as sparks from horseshoes in the streets, from the tram-lines, 



