100 YEARS AGO

Aitken (Proc. R. S. E., vol. ii p. 472, 1882) has given a complete theory of the colour of sea water as observed at various places, based upon the principle that sea water is a blue liquid. According to this view, the green tint often observed in sea water, especially near land, is to be explained by the presence of fine yellow particles. During a recent voyage by the Messageries steamer Polynesien, I was permitted, through the kindness of the Commandant Bullard, to erect a tube 736 cm. long against the rail of the after-deck, and to pass through it a continuous stream of water from the ship's salt water service. ⃛ it is useless to comment on most of the results obtained, except in so far as they give a means of easily reproducing the exact tint of pure sea water as seen through a column 736 cm. long. Make up the following solution:- Water, 500 c.c.; Soluble prussian blue, 001 gram; Saturated lime-water just precipitated by the smallest excess of bicarbonate of soda, 5 c.c.. This mixture, when viewed through a tube 18 cm. long, will show with considerable precision the colour of a sample of water from the Mediterranean, lat. 36° 24′ N., long. 17° 51′ E. of Paris.

From Nature 16 March 1899.

50 YEARS AGO

An extensive analysis of the energetic disintegrations produced in the silver and bromine nuclei of nuclear emulsions exposed to cosmic radiation indicates that the emitted particles, consisting of α-particles, protons and neutrons, generally escape from the nucleus after the excitation energy has been statistically shared among the constituent nucleons. The disintegration process is then analogous to the evaporation of molecules from a drop of liquid. Occasionally, however, stars are observed in which highly charged nuclear splinters are ejected from strongly excited nuclei before equilibrium has been attained. From a total of six thousand stars, we have observed two examples in which we can identify such heavy fragments. These events are not so rare as this might imply, since their tracks can only be identified when they have a considerable length in the emulsion. The two stars were obtained in ‘sandwich’ emulsions exposed on the Jungfraujoch (3,500 m.).

From Nature 19 March 1949.