1904-5.] Magnetic Quality in Molecular Assemblages. 1025 
Magnetic Quality in a Boscovichian Assemblage of 
Molecular Magnets. By Dr W. Peddie. 
(MS. received May 15, 1905. Read same date.) 
CONTENTS. 
Sec. Page 
1. Statement of Problem . 1025 
2. Statement of Assumptions 1026 
3. 4. Weiss’s Experimental Re- 
sults . . . 1027, 1029 
5. Wallerant’s Formula . . 1030 
6. Components of Field due to 
an Ideal Magnet . .1032 
7. Parallel Component of Force 
due to an Infinite Homo- 
geneous Assemblage . 1032 
8. Proof that 2(3 Cos 2 0 - 1) = 0 1034 
9. Modified Expression for the 
Parallel Component of 
Force .... 1034 
10. Direction Cosines of the 
Transverse Component of 
Force .... 1036 
11. Components of the Trans- 
verse Force . . .1036 
Sec. Page 
12. Modified Expressions for 
these . . . . 1037 
13. Directions of Equilibrium in 
Zero Field . . . 1038 
14. Transverse Force under 
Magnetisation in Princi- 
pal Planes . . . 1039 
15. The Magnetisation Quartic 1042 
16. 17. Magnetisation in Princi- 
pal Planes . . 1043, 1047 
18. Magnetisation and Field 
along Principal Axes . 1048 
19. Condition at a Boundary. — 
Residual Magnetisation . 1049 
20. Estimate of Size of Mol- 
ecular Magnets and of 
Molecular Susceptibility 1053 
21. Conclusions . . . 1054 
22. Approximate Evaluation of 
Constants . . . 1055 
1. The gradual growth of the theory of molecular magnetism 
from the original suggestions of Poisson and Weber is well known. 
The recent great development, made by Ewing, and tested experi- 
mentally by means of models, has placed the theory on a fairly 
firm basis, and has made essentially secure the fundamental 
postulate that magnetic phenomena in material bodies are due to 
magnetic molecules which may possibly be regarded as free from 
any directional control other than that supplied by their own 
mutual action. 
Since, on the modern view of the constitution of matter, solids 
are supposed to be aggregates of crystalline groups, the study, at 
the very outset, of magnetic quality in a crystalline medium, is a 
necessity. The fact that the more notable magnetic materials 
crystallise in forms belonging to the cubic system makes the study 
PROC. ROY. SOC. EDIN. — YOL. XXY. 65 
