Op. cit. 31, p. 152. Footnote 156: Op. cit. 31, p. 157. Footnote 157: Op. cit. 31, p. 159. Footnote 158: Connecticut Agricultural Experiment Station, Annual Report, 1888, p. 154. Footnote 159: Loughridge, Proceedings American Association for the Advancement of Science, Vol. 22, p. 81. Footnote 160: Whitney, United States Weather Bureau, Bulletin No. 4. Footnote 161: Whitney, op. cit. 40. Footnote 162: Vid. 40. Footnote 163: Vid. 40. Footnote 164: Vid. Anleitung zur Mineralogischen Bodenanalyse von Franz Steinreide; and Mikroskopische Physiographie von H. Rosenbusch. Footnote 165: Elemente einer neuen Chemisch-Mikroskopischen Mineral und Gesteinsanalyse, 1877. Footnote 166: Rosenbusch, Mikroskopische Physiographie, Plate 11, Fig. 3. The figures of crystals of potassium, sodium, calcium, magnesium, etc., are taken from the same work, Plates 10, 11, and 12. Footnote 167: Williams, American Journal of Science, February 1893, p. 203. Footnote 168: Op. cit. 46, S. 231. Footnote 169: Op. et., loc. cit. 48. Footnote 170: Op. cit. 46, S. 233. Footnote 171: Op. cit. 46, S. 235. Footnote 172: Op. cit. 46, S. 236. Footnote 173: Op. cit. 46, S. 237. Footnote 174: Op. cit. 46, S. 232. Footnote 175: Manuscript Communication from R. L. Packard. Footnote 176: Op. cit. 46, S. 241. Footnote 177: Op. cit. 46, S. 242. Footnote 178: Op. cit. 46, S. 243. NOTE.—The analyses on page 237 are by Hilgard and Loughridge from Proceedings American Association for the Advancement of Science, Portland Meeting, 1873. PART FIFTH. ESTIMATION OF GASES HELD IN SOILS. =276. Relation of Soil Composition to Gases.=—The power of a soil for occluding gases rests primarily on its composition as determined by silt analysis. The discussion of this part of the subject is so nearly related to that of the physical properties of the soil that it might properly have been included in that part of the work. Since, however, we deal in this part more with the determination of the gas constituents of the soil, it was deemed preferable to place it after the silt analysis and as introductory to the general estimation by more strictly analytical processes of the chemical constituents of the soil.