50 years ago

“Symmetry of snow crystals” — Despite an infinite variety in the patterns which appear, there does often exist a remarkable symmetry in the six rays [of snowflakes]... Since each of the six arms of the crystal would appear to be growing independently, this symmetry poses a problem in crystal growth, for it almost seems as if each arm of the six-ray star 'knows' what the other five are doing and follows suit... I conjecture that the crystal is vibrating mechanically as a flat plate, in fact as a Chladni plate, with of course a hexagonal symmetry... When the molecules adhere to achieve growth at any particular region on one arm, this immediately introduces a localized damping action on the vibrations... But this very damping is at once felt simultaneously at the corresponding positions on the other five arms. Thus molecules arrive and adhere easily at the other five arms in precisely the same situations as on the first arm; in other words, what happens on any one arm tends to be repeated on the others...

From Nature 25 January 1958.

100 years ago

The product of the world's gold mines for the year 1906 could all be packed in a room 10 feet square and 9 feet high... The value of this 90 cubic feet of gold was nearly eighty-one and a half millions sterling, and its weight nearly 674 tons... Eighty-three per cent. of the total output was secured by the Anglo-Saxon world. According to calculations and estimates made in 1900 by the director of the United States mint, the gold taken from the mines of the world since the discovery of America has amounted in quantity to about 21,424 tons... Nineteen per cent., or nearly one-fifth of the whole, has been mined in the last ten years, and nearly 30 per cent. in the last twenty years.

From Nature 23 January 1908.