Footnotes:

[1] This chapter originally appeared in Science, Vol. 49, pp. 412-417 (1919).

[2] Popular Science Review, 3, 176 (1864).

[3] Trans. Royal Scottish Soc. Arts, 4, Appendix O, 198 (1854).

[4] In the mixtures the percentages indicate proportions by weight.

[5] Succeeded Dr. John Johnson who went to the National esearch Council.

[6] At first Lt. Col. J. F. Norris was in charge of all chemical research. About December, 1917, it was divided into Offense and Defense, and Lt. Col. Lamb was placed in charge of Defense. When Col. Norris went to England as Liaison Officer, Dr. Jones took his place.

[7] At first Lt. Col. J. F. Norris was in charge of all chemical research. About December, 1917, it was divided into Offense and Defense, and Lt. Col. Lamb was placed in charge of Defense. When Col. Norris went to England as Liaison Officer, Dr. Jones took his place.

[8] At first Lt. Col. J. F. Norris was in charge of all chemical research. About December, 1917, it was divided into Offense and Defense, and Lt. Col. Lamb was placed in charge of Defense. When Col. Norris went to England as Liaison Officer, Dr. Jones took his place.