October iu, 1893J 



NATURE 



59: 



contain water in which one could sotnetimes (as in Fig. 2) 

 discern a small air-bubble. On the day when this snowfall 

 occurred the temperature was - 8^ C. Still there was a 

 continual dripping of water from the house roofs, in spite 

 of the fact that the sky was overcast, and the sun thus 

 could not contribute to melt the snow. The dripping 

 continued even at midnight in a temperature of - 12^ C. 

 Shortly after the fall of snow a transformation could be 

 observed in the crystals ; on the surface of the snow they 

 had passed from prismatic bottles to hexagonal tables 

 without any cavities. The above described fall of small 

 ice-bottles containing water, a phenomenon, as far as I 

 know, new to meteorologists, combined with the trans- 

 formation of the crystals after their descent, affords a 

 simple explanation of the fact that, in spite of the 

 severe cold, the new-fallen snow was so saturated with 

 water as to cause an incessant dripping from the roof. 



II. (a) Hexagonal Tables. 

 To the naked eye these crystals look like small, lustrous 

 scales. Their dimensions vary between o'8 and i'4 mm. 

 Under the microscope they prove to contain regular 

 cavities, remarkable as being bounded not by planes, but, 

 contrary to the accepted principles of crystallography, 

 by regularly distributed curved surfaces. The limits of 

 these cavities are shown under the microscope as fine 

 black markings, to which, on account of their resemblance 

 to forms within the organic world, I have applied the name 

 of organoid lines, cavities, and formations. The following 



Fig. 3. 



example will illustrate the structure of such crystals, 

 including such organoid cavities. The snow-crystal 

 (Fig. 3) shows in the centre a handsome star. The crystal 

 is composed of two (or more ?) superimposed tables, with 

 the same orientation. The different hexagons indicate 

 the outer limits of these tables. Two tables are united 

 by a stratum, which has the outlines shown by the stellate 

 figure. Within this figure the crystal is therefore homo- 

 geneous ; without the same, its two different layers are 

 separated by a flattened cavity, bounded by sinuate sur- 

 faces, and probably containing air. The same star in- 

 cludes some extremely regular cavities of smaller size. 

 On this table we can observe a hemihedral development, 

 the six triangular fields into which the hexagon is divided 

 by lines drawn between the centre, and the angles being 

 only alternately equal to each other. Such a hemihedry 

 is the rule in this type. It is most developed in some 

 almost triangular tables that occur among the equilateral 

 hexagons. The above described structure, two tables 

 united by a stellate layer of ice, is the general rule in the 

 tabular ice crystals. 



The organoid figures show a great multiplicity of forms, 

 but the fundamental type is the same in all of them. It 

 is evident that their outlines are fixed by certain crystal- 

 ographic laws yet unknown to us. We might possibly 



NO. 1251, VOL. 48] 



find in these organoid formations, which so strongly 

 remind us of shapes in the world of life, a clue to the 

 mathematical laws of the structural outlines of organisms. 

 Or perhaps these remarkable organoid figures are caused 

 by microscopical aerozoic organisms, around which the 

 crystals have developed. I hope next winter to be able 

 to collect observations for the answering of this question 



II. ib) Stellate Tables. 



Figs. 4-6 show some of the countless modifications 



exhibited by crystals of this type. The central table often 



shows beautiful organoid figures sometimes hemihedrally 



developed and regularly orientated cavities. Similar 



Fig. 4, 



cavities, usually of very minute size, are with great regu- 

 larity distributed in the arms of the star. 



The ramification of the plates has some connection or 

 other with the orientated cavities. Through each arm 

 of the six-sided star runs what may be called the main 

 nerve, which originates either in the central plate or just 

 outside it. This nerve is present in all the tables and 

 dendritic stars with elongated arms. The main nerve is 

 bounded by two fine, parallel gas canals. 



The first beginning of these canals consists of two or 



Fig, 



In the con- 

 ones, often 

 Owing to 



four small cavities with parallel orientation, 

 tinuation of these small cavities lie larger 

 prolongated to extended canals (^ee Fig. 4) 

 evaporation on the surface of the crystal, these canals 

 gradually become open, first at one end, and then along a 

 part or the whole of their extent, only the ridge that divides 

 them remaining as a nerve (Fig. 5). That these canals 

 are really cavities in the ice I have ascertained by observ- 

 ing and photographing snow crystals in a coloured liquid. 



