COMMENCEMENT OF WORKS. 



with, and constructed to the same section as G G I (Fig. 18). 

 This formed the final reclamation, and enabled the whole of 

 the permanent works being proceeded with. 



Portsmouth Dockyard Extension. 1 The site of these works in- 

 cluded 95 acres subject to tidal action, and covered at every high 

 water to a depth of from 7 to 10 feet. The whole area was covered 

 with very soft mud varying from 3 to 38 feet deep, the greater 

 part, however, being from 10 to 25 feet deep. This soft deposit 

 overlaid strata of the lower tertiary formation, consisting of beds 



LW.O.S.T. 



SCALE 



20 30 



FIG. 20. 



belonging to the London clay and those immediately below it. 

 All the undisturbed beds were of a solid description, varying from 

 pure hard clay to sandy strata very compact and retentive. 



The depth of the excavations varied from 40 to 65 feet. 



The method to be adopted in opening up these works, 

 covering as they did such an extended area of mainland, was a 

 matter of grave consideration. 



The original proposition was to enclose the sites of the outer 

 walls, entrances, or, in some cases, only parts of entrances, with 

 1 3l.pj.c.E.,\dL Ixiv. p. 118. 



