Every three weeks or so, owing to the constant charging and discharging and other reasons, the electrolyte in the cells, composed of sulphuric acid and water, became used up and its level sank in the cells, exposing the tops of the plates. These were no toy cells either. They stood over four feet high and were placed in the bottom of the boat, below the deck level, in two long lines strapped together with steel plates painted red and blue, indicating positive and negative. The process of topping up consisted of replenishing the water in the cells until the level covered the plates, and was usually accompanied by that of carefully wiping and cleaning the inter-cell connections, taking the densities, and generally seeing that all was in order. An unhappy seaman, clad in oilskin, was posted in the lighter to transfer his end of the rubber tube to a fresh carboy as the first was emptied and the work went merrily on. The T.I. was the mainspring of the business, while the S.T. worked under his orders, shifting the tube from cell to cell as necessary, and generally doing as he was told. He was there to learn and he knew it. When two or three cells were finished, the hatch was replaced and another lifted, and so on down one line and up the other, by which time the battery was completed, several carboys had been emptied, and eight bells had struck aboard the _Parentis_. ‘123,’ owing to a busy day, was carrying out a special routine, and the crew trooped inboard to breakfast. The rain had ceased but the prospect was still anything but cheery, and even the funny man could not brighten the settled gloom that had overcome the crew when work was restarted an hour later. The T.I. and his satellites resumed their labours by tackling the after-battery, and casting much criticism on the health of the cells and nature of the battery in general. The gun-layer, assisted by the cook, overhauled his gun, and the remainder continued their early morning tasks with more or less signs of energy. It was not a cheerful morning. By-and-by Seagrave came down, having polished off an excellent breakfast and feeling at peace with the world, to examine the work in hand and listen to the T.I.’s comments on his beloved batteries. Another hour saw the topping up completed, and a waiting tug pounced on the water-lighter and bore it away in triumph to its distant lair. Boyd appeared just as the job was finished and began to overhaul the gyro compass. While he cleaned contractors and filed transmitters he burst into ragtime, which brought Seagrave aft with a pained and virtuous expression on his face. ‘My God! Pilot,’ he said, ‘what a shine you’re kicking up. If you’d been up since seven, like I have, you wouldn’t feel so cheery. Who wouldn’t be a navigator?’ ‘Work with a will and sing while you work,’ said Boyd. ‘Work never killed the cat and I’m going to put in quite half an hour at it to-day. Our hard-worked submarine officers at their daily toil.’