August 12, 1910] 



SCIENCE 



215 



(2-3 mm. diameter), but still I gathered 

 200-300 gr. of them and immersed them — in 

 order to prevent the freezing together — in 

 glass boxes with a mixture of nearly equal 

 parts of benzol and toluol which I presumed 

 to be of a density equal to the density of hail- 

 stones, but which proved to be lighter. These 

 hailstones I brought later to Tomsk (Siberia) 

 and in December sent them to the Twelfth 

 Congress of Russian Naturalists and Physi- 

 cians in session at Moscow. These facts dem- 

 onstrate thoroughly 



Fig. 1 



servation of hailstones. My experiment has 

 also shown that it would be preferable to con- 

 serve one or two hundred hailstones separate 

 from each other, than a greater number of 

 them, partly frozen together (especially in 

 lower layers). That can be attained by in- 

 serting hailstones in some very viscous liquid 

 (cylinder oil, vaseline, castor oil) of a density 

 only nearly equal to that of hail. 



For the investigation of the microstructure 

 of a separate hailstone, Mr. W. Dudecki and 

 I made a thin section of it by at first rubbing 

 one side on emery-paper or by melting with 

 the heat of a finger. This side was laid on an 

 object-glass and frozen to it after touching 



during some time the other side of the glass 

 with a finger; the other side of the hailstone 

 was then polished in the same way as the first, 

 till the requisite thickness was attained. 

 These operations were so much easier, as the 

 temperature of air was lower — below 0°. Still 

 it was found possible to grind the hailstones 

 in a room at the room-temperature, by means 

 of cooling the object-glass, the emery-paper, 

 etc., in double-walled vessels with mixture of 

 ice and JSTaCl. 



For the optical investigation of thin sec- 

 tions was used either a polarizing microscope 



M, mirror; R, refrigerating vessel; O, objective; 

 A, analyzator. 



or a projecting lantern L (Fig. 2). In this 

 latter case the experiment was made in a lec- 

 ture-room; the section was laid in a refrig- 

 erating vessel B with double walls and with 

 double bottom (to prevent the condensation of 

 the aqueous vapor from the surrounding air) 

 of plane-parallel glass-plates; the space be- 

 tween the walls contained a mixture of ice 

 and NaCl. The real image of section was 

 projected on a screen or on a photographic 

 (" autochrom ") plate. 



The major part of the hailstones were crys- 

 tallic individuals, as also was the case with 

 " artificial hailstones " — drops of water frozen 

 in a mixture of cinnamon and linseed oil of 

 suitable density. In those hailstones, which 

 consisted of several crystallic individuals, there 

 was no regularity in the boundaries between 

 crystals in the angles between these bound- 



