Report: the hair assay

INCONCLUSIVE

LITIn 1692–93 Newton suffered a severe breakdown. P. E. Spargo and C. A. Pounds (Notes and Records of the Royal Society 34, 11–32, 1979) analysed four hairs attributed to him (one from Trinity College, one found in a book from his library, two from the Earl of Portsmouth's family) by neutron activation at Aldermaston. As summarised in the South African Journal of Science (Dec 1979): one hair segment held gold at 16 ppm (about 340× modern hair), mercury in one hair was about 38× modern, antimony about 5.5×. The authors said they had proved nothing, but called it strong circumstantial evidence for metal poisoning from his chymistry.

LIT · CRITIQUEA later reply in Notes and Records ("Newton's illness of 1692-3") objected: no contamination controls, sample masses near 10⁻¹⁰ g, and timing. Hair grows about 10 cm a year, so a lock cut at his death in 1727 cannot record 1693 unless it was cut then. The page lets you test that timing argument.

element	reported ratio to modern hair	source
Au	≈340× (16 ppm vs 0.047)	SAJS 75 (1979) summary
Hg	≈38× (one hair)	same
Sb	≈5.5×	same

MODELChoose when the lock was cut and how long it was. The strand grows at 10 cm/yr (the critic's figure); exposure years are painted along it. Only exposures inside the lock's span can be in the sample.

cut in · lock length cm assay this lock