During his return trip to the Main Base he fell through the lid of a crevasse , and was saved only by his sledge wedging itself into the ice above him .
Mawson continued the final 100 miles alone .
During Mawson 's return trip to the Main Base Mawson fell through the lid of a crevasse , and was saved only by his sledge wedging itself into the ice above him .
Mawson continued the final 100 miles alone .