On the Blockade by Oliver Optic

The Bronx was slowly approaching the steamer in the fog, which appeared to have stopped her propeller, and to be resting motionless on the long swells, hardly disturbed by a breath of air. By this time the smokestack of the Bronx was vomiting forth dense clouds of black smoke. The steamers of the navy used anthracite coal, which burns without any great volume of smoke, and blockade runners had already begun to lay in whatever stock of it they were able to procure to be used as they approached the coast where they were to steal through the national fleet. The attention of the naval department of the United States had already been given to this subject, and the first steps had been taken to prevent the sale of this comparatively smokeless coal where it could be obtained by the blockade runners.

Christy had been on the blockade; and he had been in action with a steamer from the other side of the ocean; and he knew that this black smoke of the soft coal, exclusively used by English steamers, was a telltale in regard to such vessels. It had been an idea of his own to take in a supply of this kind of fuel, for while its smoke betrayed the character of vessels intending to run the blockade, the absence of it betrayed the loyalty of the national steamers to the blockade runners. It was a poor rule that would not work both ways, and the commander of the Bronx had determined to adopt the scheme he had now put in force on board of his vessel. Although the craft on the starboard bow could hardly be distinguished in the fog, Christy had sent a trusty seaman aloft to report on the color of the smoke that issued from her funnel.