"Cloud bank," replied Peter briefly. Then in explanation he added: "There's wind behind that lot, Miss Baird; probably more than we want. It may head us too." Glancing into the compass hood to see that the girl was steering a correct course, Mostyn rapped on the thwart immediately abaft the canvas shelter in which Mrs. Shallop was either resting or brooding over more or less imaginary grievances. "We'll have to unrig the tent," he announced. "There's a stiff breeze bearing down on us." "I don't like stiff breezes," retorted the lady promptly. "I'd rather have the tent up to keep the wind out." "Sorry," replied the Wireless Officer. "It can't be done. In two minutes the lascars will commence unrigging the tent." Mostyn allowed a good three minutes to elapse before signing to Mahmed and the lascars to take down the canvas. It was an absolutely necessary step, in order to allow unimpeded access to the working canvas, should it be required either to reef the sail or stow it altogether. Having seen the task carried out, Peter proceeded to rig up a sea-anchor. "It may come in jolly useful," he remarked to Miss Baird. "If we don't want it I won't complain about useless work." With the assistance of the three Indians Mostyn bent a rope span to the yard and boom of the mizzen sail. Through the centre of each span he secured a stout grass warp, weighting the yard with the grapnel, so that, if it became necessary to ride to the improvised sea-anchor, the grapnel would keep the sail taut and in a vertical plane. By the time these preparations were completed the bank of ragged-edged clouds had covered most of the sky to wind'ard. The sun was beginning to become obscured, while there was an appreciable drop in the temperature of the air. The wind had fallen away utterly, leaving the sail hanging idly from the yard. The water no longer rippled under the boat's forefoot. All was silent save for the creaking of the mast and spars as the boat rolled sluggishly in the long, gentle swell. Keenly on the alert, Peter had taken over the helm, and was keeping a sharp look-out to wind'ard. "Down sail!" he ordered. The canvas was lowered and stowed. As a precautionary measure Mostyn had the sea-anchor hove overboard, trusting that at the first squall the high, freeboarded boat would drift rapidly until brought head to wind by the drag of the improvised floating breakwater. "It's coming," said Olive in a low voice, as a long-drawn shriek could be faintly heard--the harbinger of a vicious squall. By now it was almost dusk, so dense were the clouds overhead. The tropical sun had no power to penetrate the sombre masses of vapour. Less than half a mile to wind'ard the hitherto tranquil water was white with wind-lashed foam; while, in strange contrast, the sea-anchor was rubbing gently alongside the boat in the perfectly smooth sea.