INDEX. 



295 



Oak, 181, 134, 136 

 Ocean currents, G3 

 Open joints, danger of, in sea-works, 107- 



109, 207, 243, 244 

 Orbits of particles in waves, 23-28 

 Oregon pine, 131, 136 

 Oscillatory waves, 24-28 

 Overburden in quarries, 90 

 Over-end tipping, mound breakwaters 



constructed by, 255 

 Oxidation of iron in sea-water, 139-145 



Parapets, injurious effect of, 208 



, use of, 148 



Parkes on damage to Wick breakwater, 



84 



Particles, movement of, in waves, 23-28 

 Pell-mell block breakwaters, 208-212 



, stability of blocks in, 



214, 215 



Pentland Frith, current through, 69 

 Period of waves, 26 



, caused by earthquakes, 33 



Peterhead, early use of sloping block 



masonry at, 197 



, ground plan of harbours, 166 



, height of waves at, 35, 39 



Pholas dactylus, 112, 132 

 " Piano-blocks," used in Tyne break- 

 waters, 283 



Piers. See Breakwaters 

 Pier-heads, current liable to undermine 



or erode, 71 



, various forms of, 222-224 

 Pierres perdues block mounds, 208 

 Pile-work foundation for breakwaters, 



272 



Pitch-pine, 131, 136 

 Plymouth breakwater, 198-200 

 , effect of discarding small 



rubble, 203 



, of pitching slopes, 200 



, particulars relating to, 217 



Port Erin breakwater, 208, 214 



Port Said, advance of foreshore at, 285 



breakwater, 208, 214 



Portland breakwater, cost of staging, 245 



, particulars relating to, 216 



Portland cement, analysis of, 129 



Portland cement, core in, an element of 

 danger, 127 



, importance of thorough air- 

 slaking, 127 



, indications of good, 128 



, process of making, 124-126 



, setting of, 128-130 



should be finely ground, 127 



, specific gravity of, 128 



, strength of, 128, 129 



Precipitation, ocean currents affected by, 

 66 



Preliminary investigation of proposed 

 harbour sites, 146 



Pressure of wind, relation of, to velocity, 

 7-12 



Progress, average rate of, in constructing 

 various breakwaters, 216-221 



Proportions of ingredients for concrete, 

 115, 119-123 



Puzzuolana, injurious effect of at Holy- 

 head, 114 



used in concrete, 114, 120 



Q 



Quarrying, 89-104 



, arrangement and working of 



quarries, 91, 92 



at Holyhead, 92-96 



, blasting, 92-94, 101-104 



< , drainage of quarries, 90 



, drilling holes for charges, 96-100 



, explosives used in, 101 



, overburden, 90 



plant, 94, 95 



, seam-firing, 101 



, selection of quarry site, 89 



, " strike " and " dip " of strata, 92 



B 



" Eaces " or " roosts " of the tide, causes 



of, 69, 70 

 Range of tides, 51-54 



- in harbours, 165-167, 222-224 

 Eedman on decay of iron, 144 

 Reduction of waves, 161, 162 

 Refuge harbours, 148, 149 

 Reid on storms, 5, 19 

 Revenue, success or failure of works often 



depends upon, 286 



