[Transcriber's Notes:]

Here are all the misspelled words, odd usages and other things of note that I have found.
The word "defence", as it is spelled throughout, is time period spelling.
1 This paragraph is accurate to the book. It could read like this: "...otherwise the defences would not be being strengthened when the boys should have been making ready...".
2 The words "any one" appear to be time period usage.
3 The original does use the word "then" though it should probably be "when": "...relieved from guard duty, and when the gate had been closed..."
4 The original does use the word "and": "...the gate was barred on the inside, and Mary Pemberton standing close beside it..."
5 The original does use the word "prosecute". I suspect it is just time period usage. "...in position to prosecute their murderous work."
6 This paragraph is accurate to the book: "...there's no show of our being able to do anything here..."
7 The second "e" in the word "reechoed" is a small letter "e" with diaeresis.
8 The words "any one" appear to be time period usage.
9 The word "of" appears to be time period usage: "...uncle heard from those aboard of the last vessel...".
10 The word "resentiments" appears to be a misprint of "resentments". "...gave vent to their resentiments and rage..."
11 The words "some one" appear to be time period usage.
12 The second "e" in the word "reentered" is a small letter "e" with diaeresis. It is also used in the title of the 13th illustration.
13 This paragraph is accurate to the book: "...shake the very earth, and on the moment rain fell in torrents..."
14 The word "greal" appears to be a misprint for "great". "...the storm continued with greal fury."
15 The words "some one" appear to be time period usage.
16 The word "of" appears to be time period usage: "...to permit of a rescue..."
[End of Transcriber's Notes]