when night fell all the interior of the great dome, streets and houses, became lighted with brilliant incandescent lamps, which rendered it bright as day. dorothy thought the island must look beautiful by night from the outer shore of the lake. there was revelry and feasting in the queen's palace, and the music of the royal band could be plainly heard in lady aurex's house, where ozma and dorothy remained with their hostess and keeper. they were prisoners, but treated with much consideration.

lady aurex gave them a nice supper and when they wished to retire showed them to a pretty room with comfortable beds and wished them a good night and pleasant dreams.

"what do you think of all this, ozma?" dorothy anxiously inquired when they were alone.

"i am glad we came," was the reply, "for although there may be mischief done to-morrow, it was necessary i should know about these people, whose leaders are wild and lawless and oppress their subjects with injustice and cruelties. my task, therefore, is to liberate the skeezers and the flatheads and secure for them freedom and happiness. i have no doubt i can accomplish this in time."

"just now, though, we're in a bad fix," asserted dorothy. "if queen coo-ee-oh conquers to-morrow, she won't be nice to us, and if the su-dic conquers, he'll be worse."

"do not worry, dear," said ozma, "i do not think we are in danger, whatever happens, and the result of our adventure is sure to be good."

dorothy was not worrying, especially. she had confidence in her friend, the fairy princess of oz, and she enjoyed the excitement of the events in which she was taking part. so she crept into bed and fell asleep as easily as if she had been in her own cosy room in ozma's palace.

a sort of grating, grinding sound awakened her. the whole island seemed to tremble and sway, as it might do in an earthquake. dorothy sat up in bed, rubbing her eyes to get the sleep out of them, and then found it was daybreak.

ozma was hurriedly dressing herself.

"what is it?" asked dorothy, jumping out of bed.

"i'm not sure," answered ozma "but it feels as if the island is sinking."

as soon as possible they finished dressing, while the creaking and swaying continued. then they rushed into the living room of the house and found lady aurex, fully dressed, awaiting them.

"do not be alarmed," said their hostess. "coo-ee-oh has decided to submerge the island, that is all. but it proves the flatheads are coming to attack us."

"what do you mean by sub-sub-merging the island?" asked dorothy.

"come here and see," was the reply.

lady aurex led them to a window which faced the side of the great dome which covered all the village, and they could see that the island was indeed sinking, for the water of the lake was already half way up the side of the dome. through the glass could be seen swimming fishes, and tall stalks of swaying seaweeds, for the water was clear as crystal and through it they could distinguish even the farther shore of the lake.

"the flatheads are not here yet," said lady aurex. "they will come soon, but not until all of this dome is under the surface of the water."

"won't the dome leak?" dorothy inquired anxiously.

"no, indeed."

"was the island ever sub-sub-sunk before?"

"oh, yes; on several occasions. but coo-ee-oh doesn't care to do that often, for it requires a lot of hard work to operate the machinery. the dome was built so that the island could disappear. i think," she continued, "that our queen fears the flatheads will attack the island and try to break the glass of the dome."

"well, if we're under water, they can't fight us, and we can't fight them," asserted dorothy.

"they could kill the fishes, however," said ozma gravely.

"we have ways to fight, also, even though our island is under water," claimed lady aurex. "i cannot tell you all our secrets, but this island is full of surprises. also our queen's magic is astonishing."

"did she steal it all from the three adepts in sorcery that are now fishes?"

"she stole the knowledge and the magic tools, but she has used them as the three adepts never would have done."

by this time the top of the dome was quite under water and suddenly the island stopped sinking and became stationary.

"see!" cried lady aurex, pointing to the shore. "the flatheads have come."

on the bank, which was now far above their heads, a crowd of dark figures could be seen.

"now let us see what coo-ee-oh will do to oppose them," continued lady aurex, in a voice that betrayed her excitement.

the flatheads, pushing their way through the line of palm trees, had reached the shore of the lake just as the top of the island's dome disappeared beneath the surface. the water now flowed from shore to shore, but through the clear water the dome was still visible and the houses of the skeezers could be dimly seen through the panes of glass.

"good!" exclaimed the su-dic, who had armed all his followers and had brought with him two copper vessels, which he carefully set down upon the ground beside him. "if coo-ee-oh wants to hide instead of fighting our job will be easy, for in one of these copper vessels i have enough poison to kill every fish in the lake."

"kill them, then, while we have time, and then we can go home again," advised one of the chief officers.

"not yet," objected the su-dic. "the queen of the skeezers has defied me, and i want to get her into my power, as well as to destroy her magic. she transformed my poor wife into a golden pig, and i must have revenge for that, whatever else we do."

"look out!" suddenly exclaimed the officers, pointing into the lake; "something's going to happen."

from the submerged dome a door opened and something black shot swiftly out into the water. the door instantly closed behind it and the dark object cleaved its way through the water, without rising to the surface, directly toward the place where the flatheads were standing.

"what is that?" dorothy asked the lady aurex.

"that is one of the queen's submarines," was the reply. "it is all enclosed, and can move under water. coo-ee-oh has several of these boats which are kept in little rooms in the basement under our village. when the island is submerged, the queen uses these boats to reach the shore, and i believe she now intends to fight the flatheads with them."

the su-dic and his people knew nothing of coo-ee-oh's submarines, so they watched with surprise as the under-water boat approached them. when it was quite near the shore it rose to the surface and the top parted and fell back, disclosing a boat full of armed skeezers. at the head was the queen, standing up in the bow and holding in one hand a coil of magic rope that gleamed like silver.

the boat halted and coo-ee-oh drew back her arm to throw the silver rope toward the su-dic, who was now but a few feet from her. but the wily flathead leader quickly realized his danger and before the queen could throw the rope he caught up one of the copper vessels and dashed its contents full in her face!