Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/165

 of direction which has been preserved in so long a drill, although the junctions were made from several different points.

Second, the small number of shafts, and consequently the length of tunnel between each, which was ventilated during the progress of the work. I am inclined to believe that it exceeds in this respect all other attempts of a similar kind, and the section may therefore, in the hands of the Geological Society, be a useful document for future engineers. The means which I adopted for obtaining perfect ventilation will be found to be described in the Transactions of the Society for the Encouragement of Arts, Manufactures, and Commerce, for the year 1810.