196 
PHYSICS: A. ST. JOHN 
where <£ n Onp is tne an S le between the planes and the basal pinacoid 0001 
and K is a factor varying from pyramid to pyramid in the same model and 
with different models for the same pyramid, its value depending upon the 
grouping of the planes in a given form. Values of this quantity have been 
TABLE 2 TABLE 4 
h = 19.00 cm. h = 14.75 cm. 
INDEX 
X 
d X 10 8 cm. 
o X 10 8 cm. 
INDEX 
X 
d X 10 8 cm. 
o X 10 s cm. 
1010 
0.97 
4.13 
4.77 
0001 
0.96 
3.25 
4.78 
1.98 (2) 
4.05 
4.68 
1.92(2) 
3.24 
4.82 
2.93 (3) 
4.11 
4.74 
oilo 
1.50(2) 
4.15 
4.79 
1120 
1.70 
2.36 
4.72 
2.25 (3) 
4.15 
4.79 
3.40(2) 
2.36 
4.72 
10l2 
1.22 
2.55 
4.68 
0110 
0.95 
4.22 
4.87 
2.45 (2) 
2.54 
4.67 
1.92 (2) 
4.18 
4.82 
3034 
2.90 
1.07 
4.81 
2.90(3) 
4.15 
4.79 
1120 
2.65 (2) 
2.34 
4.68 
2110 
1.70 
2.36 
4.72 
3032 
4.5-5.2 
1.19-1.38 
3.40(2) 
2.36 
4.72 
2021 
4.80(2) 
1.30 
4.72 
1010 
1.95 (2) 
4.12 
4.76 
3031 
4.0-4.5 
0.69-0.78 
4041 
5.5-6.0 
1.04-1.13 
4. 76^0.04 
4.74±0.06 
TABLE 3 
h = 14.75 cm. 
INDEX 
* 
d X 10 8 cm. 
0 X 10 8 cm. 
2110 
1.34 
2.32 
4.64 
2.70 (2) 
2.31 
4.62 
1010 
2.20(3) 
4.25 
4.91 
3.00(4) 
4.15 
4.7-9 
1100 
1.50 (2) 
4.15 
4.79 
2110 
1.35 
2.31 
4.62 
Average 
4.73±0.10 
TABLE 5 
h = 14.75 cm. 
INDEX 
X 
d X 10 8 cm. 
0 X 10 8 cm. 
0001 
1.85 (2) 
3.38 
4.78 
2.80(3) 
3.34 
4.76 
1011 
1.5-2.0 
3.1-4.2 
5.40(6) 
3.46 
4.70 
10T2 
2.40(2) 
2.58 
4.75 
1013 
1.60 
1.94 
4.72 
3032 
2.50 
1.24 
4.70 
Average 
4.72±0.04 
determined by inspection of the models and are tabulated in table 6. The 
data of table 4 are consistent only with the distances calculated for model 
IV, which is therefore taken to represent the structure. In the tabulations 
but four models have been considered as these are all that satisfy reasonable 
considerations of symmetry. 
The, investigation shows that ice is properly assigned to the hexagonal 
system, that it consists of four interpenetrating triangular lattices, and that 
the fundamental spacings are 
