Obvious typographical errors and punctuation errors have been corrected after careful comparison with other occurrences within the text and consultation of external sources. Except for those changes noted below, all misspellings in the text, and inconsistent or archaic usage, have been retained. For example, time zone, time-zone; Le Verrier, Leverrier; light wave, light-wave; intrust; wabbling; unexcelled; crape; monumented. Pg 146, 'James Clark-Maxwell' replaced by 'James Clerk Maxwell'. Pg 189, 'impossible to measure' replaced by 'possible to measure'. End of Project Gutenberg's Practical Talks by an Astronomer, by Harold Jacoby