Experiments at Lydd, in 1886, showed that earthen parapets of sandy loam 12 feet thick were but little affected by the fire from B. L. 12-pdr. and 20-pdr. with steel shells, and the following rough rules will probably suffice against field-guns:
| For friable soil, such as sand, etc. | 2 | yards |
| For medium soil, such as ordinary earth | 2½ | yards |
| For tenacious soil, such as clay | 3 | yards |
The following data, obtained from experiments by the Germans, may prove of service:
PENETRATION FROM ARTILLERY-FIRE.
| Field-artillery. | Garrison and Siege Artillery. | ||
| Shrapnel; (bullets or fragments) in earth, | 16 to 39 in. | In earth | 39 in. |
| Shrapnel, wood, overhead cover | 2 in. | Wood, overhead cover | 4 in. |
| Individual shot: | |||
| Striking fair, earth | 39 to 79 in. | Earth | 10 to 13 ft. |
| Striking fair, brickwork | 39 in. | ||
| Striking fair, snow | about 27 ft. | ||
PENETRATION FROM INFANTRY-FIRE.
| Sand | 29½ | in. |
| Rammed snow | 6 ft. 9 | in. |
| Sheaves of grain | 16 ft. 9 | in. |
| Pine | 39 | in. |
| Steel plate | 0.8 | in. |
| Ordinary earth | 39 | in. |
| Swampy or wet ground | 79 | in. |
| Laid sods and turf | 79 | in. |
| Oak | 24 | in. |
| Brickwork | 19½ | in. |
| A double thickness of planks filled in with broken stone | 7.8 | in. |
Penetration at all ranges has been increased with the new rifle (U.S.). At 200 to 300 yards protection is afforded by about 0.2 inch of steel plate and about 0.3 inch wrought iron; at same distances penetration in earth is 25 inches, in pine, 30 inches.