50 years ago

'Recent discoveries at Olduvai Gorge, Tanganyika' By Dr. L. S. B. Leakey — Work has, in the main, been concentrated upon two sites: BK II at the lowest level of Bed II Olduvai, where it rests uncomformably upon the eroded top of Bed I, and at SHK II at a level about 10 ft. above the base of Bed II ... At each of these two sites, living floors of Chellean man have been found, with big accumulations of stone tools, waste flakes and the fossilized remains of the animals upon which Chellean man lived ... In addition [were found] ... two hominid teeth. It was hoped that this important discovery, made at the close of the 1955 season, was the precursor of further finds of hominid material, but the hope has not been fulfilled and, therefore, a preliminary description of these teeth is given here.

From Nature 19 April 1958.

100 years ago

'The condensation of helium' — In Nature of March 12 I have found a note referring to my experiments on the expansion of helium, made in consequence of my determinations on the isothermals of helium, at −252 °C. and −259 °C., which yielded nearly −5 °K. for the critical temperature of helium. The prosecution of the experiments has shown that what I observed in expanding the gas was not the evaporation of solid helium, but solution phenomena of solid hydrogen in gaseous helium. I have communicated to the Amsterdam Academy a note on my experiments, which at the moment leave the condensation of helium a yet undecided question. Of course, I have written the details to Sir James Dewar, and I hoped to do so to you to-day, but by pressing duties I cannot do it before to-night, and you will probably go to press before that letter reaches you. So I beg to be allowed to send you this first short notice.

H. Kamerlingh Onnes

From Nature 16 April 1908.