 The Brooksville Tunnel is the most difficult work of the kind , I have seen any record of : at the Western entrance , the pressure of the big slides actually causes the bottom to surge up , as is sometime the case in coal mines ; in view of the sliding tendency and immense pressure of this ground , it will be advisable to enter on that side with an invested arch to prevent a collapse ... This work is vastly more difficult than the Greenwood Tunnel was , though it was not , by any means , an easy safe job . 
