Booth’s diaries

"2 Secondly: Prince’s Lines, situated under Willis’s Batteries but is no higher from the water than 160 or 170 feet and in its length above 700 feet: the retaining part of its Glacis is an inaccessible Rock whose precipice at its lowest is about 30 ft. This Line has been cut off the Rock, and was began in the year 1720 but its breadth being so narrow that it was found very incommodious and dangerous in the last Siege of 1727, which was the reason of having it widen’d and some small Casemates built with the Parapets repaired in 1730, 1731 & 1732 and in 1749 had a large Casemate Bombproof for 50 men very dry and convenient for the Guard with a small one for Officers in case of a Siege.

At the same time the communications from the King’s Lines and Prince’s Lines was widen’d and lowered which was before almost impassable and seen into from without with two Retrenchments made, very necessary to defend the Lines, with Gates well secured with its defences and a Guard House for a Sergeant at the entrance.

The Head or extreme pt of the Lines next the Isthmus is mounted with 4 Guns and 2 more in a cover’d Casemate which sees in reverse. This Upper line is rather too high and retired to defend every particular part of the Avenue.

3 Thirdly: King’s Lines, is partly situated under the Prince’s Lines and about 90 feet high & length is not half the Upper Line. But by being not so high nor so much retired, it commands perfectly the Avenues to the Place and very well disposed to pour all the fire possible on the narrow part of the Isthmus, but owes most of the advantage to its natural situation, which is improved by a cut in the Rock in the same manner as the Prince’s Lines. It has 3 Batteries of 6 Guns in the whole and two mortars. There is a Cave in the Rock of great advantage in time of Siege to secure 100 men from shot or shells, with another lesser to keep in stores and a covered communication secured by the Rock to the Prince’s Lines. This work was made in the year 1716 but has been repaired both in its Parapet and Glacis in the Year 1732 and 1750."

Image: At the Old Mole. 1830. Whymper. Colour print showing part of the Northern Defences