THE FAUNA OF A COAL-PIT AT GREAT DEPTHS 159 



Description of Pit and Conditions of Life. All the 

 animals were collected in a limited area in one of the pits in 

 the Midlothian coalfield at Niddrie. The actual collecting 

 ground was in an incline opening off the horse-road of No. 

 13 pit, roughly a quarter of a mile from the shaft. The shaft 

 is perpendicular, and to this point 750 feet deep. The incline 

 also connects with the oblique shaft of No. 12 pit, but by a 

 complicated series of passages at different levels. It pene- 

 trates the Peacock seam of coal, and is a comparatively 

 recent working, having been opened up about 1909. There 

 is no ventilating shaft to the surface in its neighbourhood, 

 such as might have afforded access to some of the animals. 



The general conditions of life may be shortly summed up. 

 The working is a moderately narrow excavation, with walls 

 and roof partly mudstone, partly coal. These are supported 

 by close-set props of pine, and the floor is strewn with coal 

 fragments and dust, or dross. Absolute darkness reigns, and 

 the greater part of the place is damp through a constant drip 

 of water, which specially forms a moist surface on the rock 

 " pavement " left after the removal of the coal seam. Yet, 

 owing to a system of ventilation, the air is not stagnant, as in 

 a damp cellar, but blows in a fair and fresh current through the 

 workings. 



Animal Inhabitants General Remarks. In such 

 conditions the animals live, but even where there is so 

 great uniformity they show preferences of habitat. The 

 Mycetozoan naturally was confined to the pit props, the 

 " Clocker " beetle {Quedius mesomelinus), of which several 

 were seen, was found only on the floor of the working or 

 on the coal seam, the flies and the beetle Thanasimus 

 formicarius were captured during flight ; but the slugs, the 

 earthworms, the spiders, and the collembola appeared to be 

 ubiquitous, occurring on the moist " pavement " of rock, on 

 the coal face, occasionally on the floor of the road amongst 

 the dross, and on the pit props. 



Food. The food of the pit inhabitants probably resembles 

 very closely the fare of their kind above ground. The 

 presence of numbers of slugs, the first animals retrieved from 

 the depths, and the fact that they were found far from the 



