100 YEARS AGO

A remarkable paper, by Mr. Nikola Tesla, appears in the June number of the Century Magazine. The subject is “The Problem of Increasing Human Energy, with Special Reference to the Harnessing of the Sun's Energy”; and though metaphysical and sociological questions receive a large share of attention, the article contains an account of some very interesting electrical experiments… Electrical discharges capable of making atmospheric nitrogen combine with oxygen have recently been produced. Experiments made since 1891 showed that the chemical activity of the electrical discharge was very considerably increased by using currents of extremely high frequency or rate of vibration… The flame grew larger and larger, and its oxidising action more and more intense. From an insignificant brush discharge a few inches long it developed into a marvellous electrical phenomenon, a roaring blaze, devouring the nitrogen of the atmosphere and measuring sixty or seventy feet across. The flame-like discharge visible is produced by the intense electrical oscillations which pass through the coil and violently agitate the electrified molecules of the air. By this means a strong affinity is created between the two normally indifferent constituents of the atmosphere, and they combine readily, even if no further provision is made for intensifying the chemical action of the discharge.

From Nature 31 May 1900.

50 YEARS AGO

The subject of population growth or decline has been in the forefront since the Royal Commission on Population began its investigations and deliberations in 1944. Last year its final report was published, and one of its main conclusions was that the slackening of population growth was due to a change in respect of average family size. The Royal Commission outlined the historical background against which the small family came into being: the decline in the importance of the family as a productive unit, the lengthening period during which children remained dependent upon their parents, the advantages of small family size for those struggling for social security and promotion, the increasing and more widely spread knowledge of the techniques of controlled fertility, the changing status of women and the increased opportunities for the enjoyment of leisure outside the home.

From Nature 3 June 1950.