  Spectra of the QSO pair Q0307-195A,B have been obtained in the Ly-alpha
Forest (3660 - 3930 A) and C IV (4720 - 4850 A) regions with a FWHM resolution
between 0.7 and 0.5 A. 46 lines have been detected in the spectrum of object A
while 36 in the spectrum of object B, of them 29 and 20 were identified as
Ly-alpha absorptions respectively. The present observations have been
supplemented with data of comparable quality on other 7 QSO pairs available in
the literature to give an enlarged sample of 217 Ly-alpha lines with rest
equivalent width W_o > 0.3 A. The analysis of the hits (i.e. when an absorption
line appears in both QSO spectra) and misses (i.e. when a line is seen in any
of the QSO spectra, but no line is seen in the other), carried out with an
improved statistical approach, indicates that the absorbers have typically a
large size (h = H_0/100 km/s/Mpc, q_0 = 0.5): R = 362 h^{-1} kpc, with 95 %
confidence limits 298< R <426 h^{-1} kpc and R = 412 h^{-1} kpc, with 95 %
confidence limits 333< R <514 h^{-1} kpc for the radius in idealized spherical
and disc geometries, respectively. The present data do not allow to establish
any correlation of the typical inferred size with the proper separation or with
the redshift of the pairs. The correlation between the observed equivalent
widths of the absorbers in the adjacent lines of sight becomes poorer and
poorer with increasing proper separation. A disc geometry with a column density
profile N(r) \propto (r/R_0)^{-gamma}, gamma=4, is found to reasonably
reproduce the data with R_0 ~ 100-200 h^{-1} kpc, but also spherical clouds
with the same column density profile and a power-law distribution of radii may
give a satisfactory representation of the observations.
