From the site:

From the first Punch magazine in 1841 until his death in the 1864 John Leech's cartoons were a major feature. This is an online archive already containing over 600 chosen cartoons of his from Punch over the period. In general copyright only lasts until 70 years after the death of an artist so we believe all of these wonderful cartoons to be out of copyright but we obviously make no warranty to that effect.