supply of air and water, and the electric light cables for immediate connection with the caissons as soon as they should be moored in place.
THE PNEUMATIC CAISSONS; QUEENSFERRY.
_Figs._34_and_35,_Page_21.png)
Preliminary Work in Connection with the Four Queensferry Caissons.
Over the area to be occupied by these four circular piers, and to some extent outside and round it, a number of soundings were taken to ascertain the depth of water, of mud, of silt, of soft clay, and of hard clay. These data are given in another place. The T head of the jetty, which had in the mean time been completed, left four corner spaces free for the reception of the caissons, and strong timber dolphins of treble and quadruple piles were placed on three sides of the space left. As the tide currents are not nearly so strong here as on Inchgarvie, and as the caissons would almost immediately touch the soft ground during low water, the danger of their getting away was much less here, and no outside moorings were therefore provided, but strong chains fixed to the piles, and ready to be attached to lugs rivetted to
