Overcast sky prevented obtaining good observations to check the run during the minelaying, and as there was no check on latitude and the current was variable, the course was changed slightly for the last third of the run, to be sure of clearing our first field, towards which we were heading. This accounts for the bend in that line on the chart. We were crossing the 150-fathom deep water which skirts the Norway coast, three large ships, _Canonicus_, _Canandaigua_, and _Housatonic_, led by _San Francisco_, laying 2200 mines in two rows on a line 46 miles long. In spite of repeated breaking of the distance-measuring taut wire, the speed over ground was estimated closely enough to end the line within one-half mile of the point intended, which was correct within 1 per cent. There were again no casualties and all the mines were planted. Two ships planted 710 each in continuous strings, fully establishing the success of the mining installations. There was no longer any doubt of the ability of one of these ships to plant her entire load of 860 mines without break. All vessels returned to base ready for further duty. The explosions of defective mines on this excursion amounted to between 4 and 5 per cent, and reports received from British trawlers watching the first minefield indicated that enough more had gone off in that field since the first day, to bring the total there up to between 5 and 6 per cent. Despite all remedy, these explosions increased in number up to the 5th excursion. Then the cause was found to be due not to unskilful, negligent, or otherwise faulty procedure in either the ships or the bases, but to lie partly in supersensitiveness in the mines’ adjustment, partly in imperfection in manufacture—inevitable in such large numbers made under prevailing industrial conditions, especially of a new design.