3-034-769 - The Print Collector/Heritage Images

Siege Operations at Chatham: sappers working behind sap roller, 1871. British Army training. 'The operations of a party of sappers, under Lieutenant de Villamil, to exemplify the comparative efficiency of rollers and shields as protection for the men at their work, deserve a passing notice. There were "double saps," which are planned to dig trenches for the defence of the sides as well as the front of an advancing force; there were also "single saps," which provide cover for the front only. Some of the trenches were made deep enough to cover a line of troops standing; others only in a kneeling position. The "sap roller," behind which the sappers can work in greater safety near to the hostile fortifications, is merely a large gabion, or bundle, thick enough to stop a musket-ball, but which would not, of course, resist the fire of artillery. The "sap-shield," invented by Colonel Lovell, C.B., is designed to cover the men working at the head of the trench. It is a convex iron plate laid over the opening of the ground, and the man beneath is to move it forward, when needful, by raising it with his shoulder and pushing it on. Bullets and even cannon-shot would glance off from its surface; but shell falling at the side would still do harm'. From "Illustrated London News", 1871.