'Contact and electric torpedoes [mines] were both employed for the protection of the German coast during the war. The former had generally a charge of 82 lb. of powder, and were moored about 3 ft. below the surface of the water. The electric torpedoes were loaded with 220 lb. of dualin, equivalent to 1100 lb. of powder, and were fastened 8 ft. below the water. The explosion of these was brought about by means of batteries placed on the shore, and they were perfectly safe. On the other hand the contact torpedoes were exceedingly dangerous to handle, and three fatal accidents took place in lifting them from their positions.'