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Abstract. High resolution photographs of the solar chromosphere have been obtained with the 40-cm refractor of the Athens Observatory and a 0.5 A. 'Halle' Ha filter. Our best photographs show a resolution of 0".6, which is comparable with the theoretical resolving limit of 0".4, at Ha. The achieved resolution permitted us to secure some excellent observations of the fine structure of the chromosphere on the disk as well as on the limb. The study of these observations leads to the following results: (a) the bright filaments of the disturbed chromosphere as well as the penumbral ones appear to consist of knots. (b) inside the cells of the chromospheric network of the quiet chromosphere, bright roundish granule-like formations are present, their mean size being of the order of 2500 km. (c) the bright fine mottles seem to lie at the root of the elongated dark ones, each pair of them giving rise to a spicule.

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Some properties of the solar spicules as observed outside the limb through a Halle K-filter at the centre of the line are investigated. The observations have been made at the Pic-du-Midi Observatory. The results are as follows: (a) The chromosphere at the limb appears more diffuse in the K line than in the Hc~ line, the spicules being not well resolved. (b) The ratio of spicule intensity to the background intensity increases with height, as in the case of Ha spicules, but it is, in every height, smaller than that in Ha. (c) The spicule mean width is measured photometrically and found equal to 1900 km. (d) The lifetime is found to be 4.5 rain. (e) The mean chromospheric height is estimated to be 6.000 km.