152 JOHANNES GRUNOW 
were used. In the rate of growth of different types 
of crystals (such as dendrites and needles) differ- 
ences exist because of variations of the vapor 
pressure along the path. Assuming a constant 
mean value for the rate of growth, as it was done 
here, the determination of the thickness of layers 
becomes somewhat doubtful, but is unavoidable. 
Losses of substance by evaporation in case the 
erystal passes through possibly existing dry lay- 
ers, however, can be seen by the degenerated 
shape of the crystal. Those particles remain un- 
considered. By picking out the largest of each 
type from among all crystals, with a sufficient to- 
tal number of the same, it can be assumed that 
the size thus found presents a characteristic meas- 
ure for the thickness of the layer within which 
the crystal originated. 
With the rate of fall V, the rate of growth W, 
and the size of the crystal AG, the thickness of 
layer H is thus calculated, 
AH = (V-AG/W) (m) 
After analysing the different snow crystals con- 
tained in the snow sample for each observation 
term according to this procedure, the ranges ob- 
tained for the temperature and the thickness of 
Fic. 2—Construction of a height cross section of temperature and humid- 
ity; March 20, 1958, O8h 34m GMT (Operation 26) 
