Changed "day-light" to "daylight" on page 77: "see them by daylight."
Changed the second question numbered 40 to "41" from page 79.
Changed "eliptical" to "elliptical" on page 83: "they were elliptical."
Capitalised "Mercury" on page 83: "made upon Mercury."
Added question mark on page 84 after "those beautiful lines of Milton."
Removed repeated word, "it", on page 88: "provided it were steady."
Changed "aeriform" to "æriform" on page 136 (in versions supporting full Latin-1 character set).
Changed "atmospherical" to "atmospheric" on page 139: "the atmospheric air."
Changed "rarifies" to "rarefies" on page 140: "heat rarefies air."
Changed "to day" to "to-day" on page 157: "our lesson to-day."