Illustrations (or Plates) which interrupted paragraphs have been moved to more convenient positions between paragraphs.

A few words appear in both hyphenated and unhyphenated versions. A couple have been corrected, for consistency; the others have been retained.

Page x: 'XI' corrected to 'IX'

"IX. THE ASTEROIDS 148"

Page 4: Corrected 'lengthwas' to 'length was'.

"... with a glass whose focal length was 212¼ feet."

Page 25: 'familar' corrected to 'familiar'.

"... or, to use more familiar terms,..."

Page 90: "... more especially if the object casting the shadow have a sharply defined edge,..."

'have' is correct, and has been retained (subjunctive after 'if').