"Golly! I hope dis chile ain't goin' to git in no subicecream ship what'll stay down under de water so de fishes gits him!" exclaimed Washington, opening his eyes wide. "Dat's worser dan freezin!"
"Can't you swim?" asked Mark with a wink at Jack.
"Co'se I can swim, boy. I can swim like a starfish, but I can't wif ten thousand tons of a subicecream ship on my back."
"A sub-ice-cream ship is a new one," commented the professor with a smile. "It's a submarine, Washington."
"I can't see no difference," persisted the colored man. "Subicecream am good enough for me."
That night Mark and Jack were thinking so much of the proposed test of the ship the next day that they each dreamed they were sailing beneath the waves, and Jack woke Mark up by grabbing him about the neck during a particularly vivid part of the vision.
"What's the matter?" inquired Mark, sleepily.
"I thought the ship turned over and spilled me out and I was drowning," explained Jack. "I grabbed the first thing I got hold of and it happened to be you."
"Well, as long as you're safe you can go to sleep again," said Mark. "I dreamed I was chasing a whale with the Porpoise."
The boys were up early the next morning, and found the professor and Washington before them. The inventor was inspecting the track which had been built from the shed down to the water's edge to enable the Porpoise to slide into the ocean.