  We investigate gradient of magnetic field across neutral lines (NLs), and
compare their properties for NLs with and without the chromospheric filaments.
Our results show that there is a range of preferred magnetic field gradients
where the filament formation is enhanced. On the other hand, a horizontal
gradient of magnetic field across a NL alone does not appear to be a single
factor that determines if a filament will form (or not) in a given location.
