We present results of a method for an automatic search for H i shells in 3D data cubes and apply it to the Leiden-Dwingeloo H i survey of the northern Milky Way .
In the 2nd Galactic quadrant , where identifications of structures are not substantially influenced by overlapping , we find nearly 300 structures .
The Galactic distribution of shells has an exponential profile in the radial direction with a scale length of \sigma _ { \mathrm { gsh } } = 3 kpc .
In the z direction , one half of the shells are found at distances smaller than 500 pc .
We also calculate the energies necessary to create the shells : there are several structures with energies greater than 10 E _ { \mathrm { SN } } but only one with an energy exceeding 100 E _ { \mathrm { SN } } .
Their size distribution , corrected for distance effects , is approximated by a power-law with an index \alpha = 2.1 .
Our identifications provide a lower limit to the filling factor of shells in the outer Milky Way : f _ { \mathrm { 2 D } } = 0.4 and f _ { \mathrm { 3 D } } = 0.05 .