Spectra of the QSO pair Q0307-195A , B have been obtained in the Ly \alpha forest ( 3660–3930 Å ) and C iv ( 4720–4850 Å ) regions with a FWHM resolution between 0.7 and 0.5 Å .
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 } \geq 0.3 Å .
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 Throughout this paper we will assume : h \equiv H _ { 0 } / ( 100 km s ^ { -1 } Mpc ^ { -1 } ) , 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 of 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 } \simeq 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 .