482 
PllOFESSOR HENRY A. MIERS: AX ENQUIRY INTO 
At 2.30 A.M., t = 17°'9, tlie readings were 
356° 
21', 
0 
= 356° 
154', 
oo^ 
= 0° 
O', 
356° 
12 V, 
A 
301° 
36', 
^'^a/3 
247° 
41' 
0) 
= 246° 
56f', 
= 0° 
15', 
"v 
246° 
41 f', 
- ^ ap 
67° 
O', 
/ 
(O 
= 66° 
04V, 
/ / 
0^ 0^ y 
= 0° 
11 4' 
^ ^ 3 
G6° 43'. 
Ill addition to these images there were also three close to and oi^, and 
proceeding from the lower part of the face (tig. 13); calling these wi and w,., the 
following measurements were obtained ;— 
At 2.30 A.M. 
“A 301° 351', 
(Dc 240'' 47^', 
_ai^24G°41f. 
At 2.55 A.M., t — 17'2° 
“A 301° 36^', 
247° 71-', 
oic 24G° 4G|-', 
' w, 24G° 40|', .-. cu = 24G° 581'. 
ojoj^ = O'” 17i' 
So that " and a, l>, c is a Hatter form than a, A, y. 
1 J 
Oliservations of Gouy and CifAPERON and others have shown tliat solutions are 
more concentrated in their lower than in their upper layers, and this is of course the 
case in the present ex])eriments where crystals lie at the bottom of the trough. 
The case just quoted, and others like it, suggest that the vicinal form is flatter 
where the solution is more concentrated. Accordingly many experiments were made 
in which the trough wms successively raised and lowered in order to ascertain the 
eflect of immersing the same crystal to a greater or less depth in the solution. 
A crystal of potash-alum gave I'eadings 
290° 58^', 
,_o^ 290° 511'. 
When immersed deeper they ])ecame 
OyOap = 0° 7', 
