They would often crawl on their hands and knees in long drifts, or passageways, in horizontal coal layers that in some places measured just over two feet [70 cm] high.
ولا يتعدى ارتفاع هذه الانفاق في بعض الامكنة الـ‍ ٧٠ سنتيمترا تقريبا .‏