Words may have multiple spelling variations or inconsistent hyphenation in the text. These have been left unchanged, as were obsolete and alternative spellings. Misspelled words were corrected. Words and phrases in italics are surrounded by underscores, _like this_. Those in bold are surrounded by equal signs, =like this=. Obvious printing errors, such as partially printed letters and punctuation, were corrected. Final stops missing at the end of sentences and abbreviations were added. Duplicate words at line endings were removed. Figure 143 is missing in the original. Missing words [in brackets] added to text: ... kite would be adjusted [as in] Fig. 92, ... ... =A biplane= is shown [in] Fig. 211 ...