9 6 



HARBOUR CONSTRUCTION. 



Holyhead was five feet per week, four men being employed. 

 The cost varied from 10s. to 25s. per lineal foot. 



Much labour and expense will be saved by placing the charges 

 well below the level of the quarry floor say from 3 to 4 feet. 

 If this be not clone, inconvenient peaks or lumps of rock will 



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-^ T-T-^L _- -^--=-^=^==.-.-" 



FIG. 1?. Plan showing arrangement of galleries, etc., for large blast at Holyhead Quarries. Height of 

 face, 115 feet ; length of face, 210 feet; length of heading, 125 feet ; depth of sink, 23 feet, being 

 3 feet below level of quarry floor. Length of chambers No. 1, 12 feet; No. 2, 12 feet; No. 3, 

 6 feet; No. 4, 15 feet. Charges No. 1, 4200 Ibs. ; No. 2, 4500 Ibs. ; No. 3, 2300 Ibs. ; No. 4, 

 5000 Ibs. ; total, 16,OiO Ibs. Line of least resistance, average 23 feet. Produce, 120,000 tons. 



remain, which may subsequently have to be removed at con- 

 siderable cost. 



If the quarry floor is kept well below that upon which the 

 cranes and waggons travel, in the manner before mentioned, no 

 inconvenience from this cause will be experienced. 



Boring Holes for Charges. This is generally done either with 



