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    Naturevolume 417page805 (2002) | Download Citation


    100 YEARS AGO

    Mr. Marconi brought forward two interesting pieces of information in his lecture at the Royal Institution last Friday. The first relates to the new form of magnetic detector which he has been employing in place of the coherer. The instrument is found to be more sensitive and trustworthy than the coherer, and gives promise of a great increase in the speed of working. Already a speed of thirty words a minute has been attained, and this may possibly be increased to several hundred. The second point relates to the recent Transatlantic signalling. It seems that on the occasion of Mr. Marconi's journey across the Atlantic in the Philadelphia, the signals transmitted during the day failed entirely at a distance of 700 miles, although a message was successfully sent at night more than 1550 miles, and a signal more than 2000 miles. This effect Mr. Marconi suggests may be due to the diselectrification of the aërial waves by the daylight. The difficulty can, however, be got over by the use of greater transmitting power — as is evidenced partly by the fact that the signal received at Newfoundland was transmitted during the daytime.

    From Nature 19 June 1902.

    50 YEARS AGO

    It is known that the isotopic composition of carbon in living matter and related materials is different from that in carbonates. About a hundred plants, representing most of the major plant groups, have been investigated... Various hypotheses have been postulated in order to explain the results, and they can easily be described in terms of the 'local carbon dioxide cycle', well known to botanists and geochemists. It is assumed that there is a difference in the rate of assimilation of the light and the heavy carbon dioxide molecules. This difference is accentuated by the cycle: 'local air'–plant–soil–'local air', which works as an isotope enrichment process, assuming that there is an exchange between the 'local' air and the 'main' atmospheric air. At places where this cycle is intense the isotope effect is large; where it is almost absent, for example, in deserts or very windy places, the isotope effect will be small... These results are also of some interest in connexion with the carbon-14 method for age determinations. The observed effects will be accentuated because the difference in rates of assimilation will be much larger.

    From Nature 21 June 1952.

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