Proc. Roy. Soc. PJdin.'] 
[Yol. XLII. 
Fig. 7. — Helmholtz coils and turn-table for experiments on the rupture 
of pairs and rows of magnets. 
Fig. 13. — Model with magnets grouped in one plane. 
Fig. 20. — One-plane model with elliptical coils. 
Sir J. A. Ewing. 
[Plate I. 
