100 YEARS AGO

The excavations [of Stonehenge] produced clear evidence touching the mode of erection... (1) The ground on the site it was to occupy was removed, the chalk rock being cut into in such a manner as to leave a ledge, on which the base of the stone was to rest, and a perpendicular face rising from it, against which as a buttress one side would bear when set up. From the bottom of this hole an inclined plane was cut to the surface, down which the monolith which had already been dressed was slid until its base rested on the ledge. (2) It was then gradually raised into a vertical position by means first of levers and afterwards of ropes. The levers would be long trunks of trees, to one end of which a number of ropes were attached... (3) As the stone was raised, it was packed up with logs of timber and probably also with blocks of stone placed beneath it. (4) After its upper end had reached a certain elevation, ropes were attached to it, and it was then hauled by numerous men into a vertical position, so that its back rested against the perpendicular face of the chalk which had been prepared for it.

From Nature 9 February 1905.

50 YEARS AGO

“Symposium on Genetics of Population Structure.” Besides six papers, the Proceedings of the Symposium contain short comments by Dobzhansky, Lerner and Epling, the conclusions by Buzzati-Traverso and the scholarly but delightful address of thanks by Haldane... Scossiroli reported on the results of selection for bristle number in Drosophila populations after heavy X-ray irradiations... there occurred a spectacular response to selection in the ‘high’ direction but not in the ‘low’ one... It could be that X-ray-induced inheritable variation is mainly in the direction opposite to that for which natural selection had to work harder— a point well worth investigation at the threshold of the atomic age... The summing up... clearly showed how far the classic theoretical framework of population genetics has led... This change in outlook is essentially a shift of emphasis from the single gene to the integrated systems of chromosomes, the genotypes of the individuals and the whole gene pool of populations.

From Nature 12 February 1955.