212 
this sense we could say after A. Wegener that the 
development of photomicrography hindered the study 
of snow crystals. The author, therefore, has always 
tried to attach equal importance to every type of 
crystal actually observed in nature. 
General Classification for Scientific Purposes. The 
general classification presented in Table I is more or less 
similar to that of Hellmann and Nordenskjéld, but the 
special feature is the addition of new types and the 
CLOUD PHYSICS 
various forms and structures are observed only slightly 
less rarely than regular hexagonal ones. They are caused 
by asymetrical growth of branches, malformation by 
attachment of nuclei, overlapping of several planes, 
\/-shaped notch in the plate, etc. 
5. Spatial hexagonal type, P5a. This is composed of 
a base crystal of dendritic form with many branches 
attached at various points of the base crystal and ex- 
tending upwards. 
Fria. 15.—Sketches of all types of crystals in the general classification. 
alteration in some items of the classification on the 
basis of crystalline structure. The graupel (snow pellet) 
is included, because it is an extreme case of the rimed 
crystal of spatial structure. 
The sketches of all types of crystals in the general 
classification are shown in Fig. 15. A brief explanation 
will be given for some items in the general classification. 
1. Needle crystals, NV. Considering the results of the 
experiments on the artificial production of needle crys- 
tals, this should be taken as a kind distinct from the 
elongated column. 
2. Crystals with an irregular number of branches, 
P2. Crystals which look as if they had developed from 
two nuclei or in parallel growth are observed in fairly 
large numbers. They have the appearance of a twin 
crystal. This twin crystal can easily be separated by a 
shght external force, giving the three-branched, four- 
branched, and other types. Seven pairs of components 
can be expected, as shown in Fig. 16. All of these com- 
ponent crystals have been actually observed in ap- 
preciable quantities. 
3. Crystals with twelve branches, P3. This type is 
composed of two overlapping component crystals, and 
can be separated into ordinary hexagonal crystals. 
4. Malformed crystals, P4. Malformed erystals of 
6. Spatial assemblage of radiating type, P5b. This 
type has dendritic branches radiating in space from the 
center. The central part is a combination of small 
sectors or columns. The heavy snowfall in Japan is 
composed mostly of the spatial crystals, P5a and P5b. 
ona a el le 
2 3 4 5 6 7 
Fic. 16.—Seven modes of separation of a twin crystal. 
7. Capped column, CP. This is a crystal composed 
of a hexagonal column with plane crystals at both ends. 
We can find some examples of this crystal in the 
sketches by Descartes. 
8. Irregular assemblage of columns and plates, CP3. 
The ‘flour snow” frequently observed in the Alpine 
regions is an agglomeration of minute crystals of this 
type. 
9. Columnar crystals with extended side planes, S. 
The structure of this type has not yet been completely 
clarified, but experiments with artificial snow show that 
