Effect of explosion:--The submarine mine at 80' distance was completely destroyed; the dome of its circuit closer was dented in. 2ND EXPERIMENT. Countermine:--As before, but moored 27' below the surface. Submarine mines:--As before, but moored at distances of 70' to 120' from the countermine, and 27' below the surface. Effect of explosion:--The submarine mine case at 120' distance was dented, but remained water-tight; the copper guard of fuze piece collapsed, and the earth connection of the fuzes was ruptured; the dome of its circuit closer was dented. 3RD EXPERIMENT. Countermine:--As before, but moored 47' below the surface. Submarine mines:--As before, but moored at distances of 70' to 200' from the countermine. Effect of explosion:--The submarine mine case at 200' distance was dented, but it did not leak. 1ST EXPERIMENT. _Experiments at Stokes Bay, England, 1873._--Countermine:--500 lbs. of gun-cotton, enclosed in a 3/16" iron case. It was placed on the ground, in 47' of water. Submarine mines:--Six ground mines, 1/4" thick cases, fitted with circuit, 10' below the surface, at distances of 100' to 200' from the countermine. Effect of explosion:--Submarine mines at 100' and 120' distance were destroyed, and their circuit closers thrown out of adjustment; submarine mines at 140' and 170' distance were much bulged, and leaked, and their circuit closer spindles were bent; submarine mine at 200' distance was uninjured, but its circuit closer was thrown out of adjustment. 2ND EXPERIMENT. Countermine:--100 lbs. of gun-cotton enclosed in case, thickness No. 12 B. W. G. It was moored 10' below the surface, in 35' of water. Submarine mines:--Five similar mines placed at same depth, at distances of 50' to 150' from the countermine. Effect of explosion:--The submarine mine at 50' distance showed continued or dead earth, two screws broken, and its case dented; the other mines were uninjured. 1ST EXPERIMENT. _Experiments at Carlscrona, Sweden, 1874._--Countermines:--226 lbs. of dynamite, enclosed in a case 17-1/2" × 20" × 1/8". It was moored 9-3/4' below the surface, the depth of water being 41 feet. Submarine mines:--(_a_) cast iron ground 600 lb. mines, dome shaped, 48-3/4" × 21-1/2" × 2"; (_b_) cylindrical cases, wrought iron, empty, 11-1/2" × 11-1/2" × 1/8"; (_c_) cylindrical cases, wrought iron, charged, 11-1/2" × 11-1/2" × 1/8"; (_d_) cylindrical cases, wrought iron, 30-1/4" × 30-1/4" × 1/8"; (_e_) spherical cases, wrought iron, 32-1/2" × 1/8"; (_f_) spherical cases, tinned steel, 12" × 1/8". Effect of explosion:--(_b_) mine, at 34' distance, was destroyed, and one at 92' distance was slightly bulged; (_c_) mine, 58' distance, mouthpiece injured and case leaky; (_d_) mine, 244' distance, a rivet started. 2ND EXPERIMENT. Countermine:--As before, but moored at 29-1/4' below the surface; depth of water, 41 feet. Submarine mines:--As before.