[Footnote A: Presented at the meeting of May 18th, 1910.]
[Footnote B: _Transactions_, Am. Soc. C. E., Vol. LX, p. 1.]
[Footnote C: _Engineering News_, July 1st, 1909.]
[Footnote D: From "Gravel for Good Roads."]
[Footnote E: _Transactions_, Am. Soc. C. E., Vol. LXVIII, pp. 58-60.]
[Footnote F: "Discoveries and Inventions of the Nineteenth Century," by
Robert Routledge, Assistant Examiner in Chemistry and in Natural
Philosophy to the University of London.]
[Footnote G: _Engineering News_, January 15th, 1909.]