Chapter 21

CHAPTER XXI.

NOVEMBER 21st to 24th.--There was assuredly no time to be lost
before we ought to leave Ham Rock reef. The barometer had been
falling ever since the morning, the sea was getting rougher, and
there was every symptom that the weather, hitherto so favourable,
was on the point of breaking; and in the event of a gale the
"Chancellor" must inevitably be dashed to pieces on the rocks.

In the evening, when the tide was quite low, and the rocks
uncovered, Curtis, the boatswain, and Dowlas went to examine the
ridge which had proved so serious an obstruction, Falsten and I
accompanied them. We came to the conclusion that the only way of
effecting a passage was by cutting away the rocks with pikes over
a surface measuring ten feet by six. An extra depth of nine or
ten inches would give a sufficient gauge, and the channel might
be accurately marked out by buoys; in this way it was conjectured
the ship might be got over the ridge and so reach the deep water
beyond.

"But this basalt is as hard as granite," said the boatswain;
"besides, we can only get at it at low water, and consequently
could only work at it for two hours out of the twenty-four."

"All the more reason why we should begin at once, boatswain,"
said Curtis.

"But if it is to take us a month, captain, perhaps by that time
the ship may be knocked to atoms. Couldn't we manage to blow up
the rock? we have got some powder on board."

"Not enough for that;" said the boatswain.

"You have something better than powder," said Falsten.

"What's that?" asked the captain.

"Picrate of potash," was the reply.

And so the explosive substance with which poor Ruby had so
grievously imperilled the vessel was now to serve her in good
stead, and I now saw what a lucky thing it was that the case had
been deposited safely on the reef, instead of being thrown into
the sea.

Picric acid is a crystalline bitter product extracted from coal-
tar, and forming, in combination with potash, a yellow salt known
as picrate of potash. The explosive power of this substance is
inferior to that of gun-cotton or of dynamite, but far greater
than that of ordinary gunpowder; one grain of picric powder
producing an effect equal to that of thirteen grains of common
powder. Picrate is easily ignited by any sharp or violent shock,
and some gun-priming which we had in our possession would answer
the purpose of setting it alight.

The sailors went off at once for their pikes, and Dowlas and his
assistants, under the direction of Falsten, who, as an engineer,
understood such matters, proceeded to hollow out a mine wherein
to deposit the powder. At first we hoped that everything would
be ready for the