We have received several papers by Prof. Sommerfeld, dealing with the theory of the diffraction of Röntgen rays. One of these is published in the Zeitschrift für Mathematik und Physik, xlvi. I, 2, and abstracts are also given in the Physikalische Zeitschrift, ii. The special problem which forms the subject of Prof. Sommerfeld's work is the mathematical investigation of the results of the hypothesis put forward by Wiechert and Stokes, according to which Röntgen rays consist in an impulsive disturbance propagated through the ether. The author considers the problem of diffraction past a screen in the form of a half-plane and allied problems, and compares his results with those found by Haga and Wind and others. The single non-periodic impulse may be said to represent one extreme case of ray-propagation, while the purely periodic wave represents the other extreme. While actual Röntgen rays and light rays probably only approximate to these extreme cases, the agreement between Prof. Sommerfeld's conclusions and experimental results affords considerable evidence in favour of the above theory of Röntgen rays.

From Nature 8 August 1901.


It has generally been assumed that the only carboxylic acid present in the fruit of Bramley's Seedling apple is malic acid; but in 1949, when examining chromatograms run in n-butanol-formic-acid-water (40 : 10 : 50 v/v) of methyl alcohol extracts of pulp tissue of young Bramley's Seedling apples, we noted that several spots having an acid reaction to bromophenol blue appeared on the chromatograms. In addition to a relatively large spot corresponding with malic acid (RF = 0.49), there appeared a second well-defined spot (RF = 0.18) and traces of a third spot (RF = 0.07). It was possible to wash some of the acid (RF = 0.18) from the chromatogram and carry out tests on the solution so obtained... It would appear, therefore, that the new acid might well be a dihydroxy tricarballylic acid. The acid appeared to decrease in amount as the fruit ripened and also appeared to be present in the pulp of the fruit of peach and plum. One of us has since examined other varieties of English apples for the presence of the new acid. It has been found in much greater quantity in young Worcester Pearmain and young Cox's Orange Pippin apples.

From Nature 11 August 1951.