The English method of tunneling through soft ground, as its name implies, originated in England, where, owing to the general prevalence of comparatively firm chalks, clays, shales, and sandstones, it has gained unusual popularity. The distinctive characteristics of the method are the excavation of the full section of the tunnel at once, the use of longitudinal strutting, and the alternate execution of the masonry work and excavation. In America the method is generally designated as the longitudinal bar method, owing to the mode of strutting, which has gained particular favor in America, and is commonly employed here even when the mode of excavation is distinctively German or Belgian in other respects. [Illustration: FIG. 84.--Diagram Showing Sequence of Excavation in English Method of Tunneling.] =Excavation.=--Although, as stated above, the distinctive characteristic of the English method is the excavation of the full section at once, the digging is usually started by driving a small heading or drift to locate and establish the axis of the tunnel, and to facilitate drainage in wet ground. These advance galleries may be driven either in the upper or in the lower part of the section, as the local conditions and choice of the engineer dictate. Whether the advance gallery is located at the top or at the bottom of the section makes no difference in the mode of enlarging the profile. This work always begins at the upper part of the section. A center top heading is driven and strutted by erecting posts carrying longitudinal bars supporting transverse poling-boards. This heading is immediately widened by digging away the earth at each side, and by strutting the opening by temporary posts resting on blocking, and carrying longitudinal bars supporting poling-boards. This process of widening is continued in this manner until the full roof section, No. 1, Fig. 84, is opened, when a heavy transverse sill is laid, and permanent struts are erected from it to the longitudinal bars, the temporary posts and blocking being removed. The excavation of part No. 2 then begins by opening a center trench and widening it on each side, temporary posts being erected to support the sill above. As soon as part No. 2 is fully excavated, a second transverse sill is placed below the first, and struts are placed between them. The excavation of part No. 3 is carried out in exactly the same manner as was part No. 2. The lengths of the various sections, Nos. 1, 2, and 3, generally run from 12 ft. to 20 ft., depending upon the character of the soil.