100 YEARS AGO

The question as to the origin of the energy possessed by the Becquerel rays is one of considerable interest. The existence of substances capable of emitting radiations possessing energy, without any appreciable loss of weight or introduction of work from external sources, would appear to be impossible from the view of conservation of energy. The measurements of M. Henri Becquerel upon the deviation of the radium rays in an electric field, taken in conjunction with those of M. and Mme. Curie of the charges carried by these rays, lead to results which show a way out of the difficulty, on account of the extreme minuteness of the quantities of energy in question. The calculations of M. Becquerel show that this energy is of the order of one ten-millionth of a watt per second. Hence a loss of weight of about a milligram in a thousand million years would suffice to account for the observed effects, assuming the energy of the radium to be derived from an actual loss of material.

From Nature 5 April 1900.

50 YEARS AGO

Preliminary trials during the past two years, which aimed at replacing costly cultivations in root crops by chemical methods of weed control, have now been completed at Jealott's Hill. iso-Propylphenylcarbamate, 'Methoxone' and 2,4-dichlorophenoxyacetic acid were known to prevent the germination of certain plant species when applied as pre-emergence dressings, and the species response to iso-propylphenylcarbamate was different from that of the other two compounds. Therefore, mixtures of iso-propylphenylcarbamate with ‘Methoxone’ and 2,4-dichlorophenoxyacetic acid were examined alongside pre-emergence dressings of the individual components. The applications were made at different intervals prior to sowing, and these were followed by observations on subsequent crop-growth and weed-control. The main experiments were on kale and mangolds; but lettuce, onions, field beans, peas, lucerne, sugar beet and swedes were included in the second year. The preliminary trials are being extended to cover a range of soil and climatic conditions; but, although the conclusions are only tentative, they point to new possibilities of weed control in crops where at present few chemical methods are available.

From Nature 8 April 1950.