Because Hair's drawings are today the only extant visual record of how many of these sites looked, they now also have considerable historical importance. Atkinson noted that of the colliery scenes Hair depicted only one was still (partially) intact by the 1960s – the Friar's Goose pumping-engine house above Gateshead – still in operation when Hair drew it, but ruined by the mid-20th century. From this it was possible to make an assessment of the technical accuracy of Hair's drawings. Atkinson noted that "what remained of the engine-house suggests that Hair's detailed observation may be depended upon, and one would only add that he obviously tended to elongate his vertical structures". Atkinson speculates that "this was an unconscious attempt to emphasise the verticality of so many tall buildings, chimneys and the like, and with this one reservation one feels confident in looking upon these illustrations as closely observed and reasonably accurate portrayals of the contemporary scene".
