Edinb.
Tuesday 4 April
My Dear Charles
Today we had some good Expts at Professor Tait’s, <1> and one which I proposed proved a success. The subject was Vibration. A square brass plate was fastened on an upright rod by a screw in its centre then it was set into vibration by the Bow of a Violin. A mixture of powdered glass and Lycopodium seed was scattered on the plate, which immediately separated, the glass arranging itself along the 2 lines AB, CD the lycopodium assuming the form of 4 circles in the middle of each compartment. When we had studied this for some time I proposed to try what would be the effect of scattering iron filings on the vibrating plate, & then presenting a magnet. We immediately discovered a remarkable phenomenon. When the magnet was held above the iron filings they congregated into a heap immediately beneath it, but when the magnet was presented beneath the brass plate, the filings fled from it and formed a ring, leaving a vacant space in the centre. Professor Tait immediately formed a theory, why this ought to occur, but I am not sure that it was satisfactory. He is going to try bismuth powder which is a diamagnetic substance and is therefore expected to behave quite differently. I thought you would like to have a short account of our séance. I have not left myself room for other matters I return to Lacock soon, perhaps on the 11th
Your affte
Father
[envelope:]
C. H. Falbot Esqre
Llandaff
Glamorganshire
Notes:
1. Prof Peter Guthrie Tait (1831–1901), Scottish mathematician.