21. Sails made of reeds spun around a vertical shaft . 22. But there are about 27 visible vertical shafts or air vents inclusive of branch gallery. 23. The mine is developed mainly through two vertical shafts up to 22nd level at present. 24. Work began in February 1825, by sinking a diameter vertical shaft on the Rotherhithe bank. 25. A raise is often a 6 12 foot square vertical shaft divided into two sections. 26. The steering column was inclined backwards unlike the vertical shaft on many of its contemporaries. 27. Steel plates are used primarily on horizontal shafts, but are used on vertical shafts occasionally. 28. Vertical shafts were sunk to reach the deeper seams.29. The excavated material is usually transported by means of leather bags up the vertical shafts . 30. Power was transmitted by a main vertical shaft with bevel gears to the horizontal shafts.
