50 Years Ago

Interference between plant viruses was first demonstrated in plants infected with tobacco mosaic virus. Although several theories have been proposed to explain interference ... there is little evidence on the mechanisms involved. In the experiments described below interference was measured by the ability of an inoculum that does not produce local lesions (interfering strain) to affect the local lesions produced by another strain when the two are inoculated simultaneously to susceptible leaves ... The present results suggest that sap from virus-infected plants contain, in addition to infective particles, another factor that inhibits infection ... Centrifugation ... showed that infectivity and interfering activity occurred in the same zone in the gradient. If interference systems occur, then these appear to be in some way associated with virus particles.

A. D. Thomson

From Nature 27 August 1960.

100 Years Ago

On August 20 occurred the bicentenary of the birth of Thomas Simpson, who may be regarded as one of the last of the English school of mathematicians of the eighteenth century. Newton, Halley, the Gregories, Muston, Demoivre, Brook Taylor, Maclaurin, had all passed away before Simpson reached middle age ... With the sole assistance of Edmund Stone's translation of l'Hôpital's “Analyse des Infiniments Petits,” Simpson wrote “A New Treatise on Fluxions,” which was considered a notable contribution to the literature of that comparatively new subject. In 1743 ... Simpson obtained a post as professor of mathematics at the Royal Military Academy, Woolwich ... After holding his post at Woolwich for eight years, he was seized with illness, caused, it was thought, by overwork ... He journeyed to Bosworth in February, 1761, and died there on May 14.

From Nature 25 August 1910.