_Phosphatic Guanos._ Phosphoric } { Tricalcic acid } = { phosphate. per cent. per cent. Maracaibo, or Monks 42 92 Raza Island 40 87 Curacao 40 87 _Baker Island_ 39 85 Starbuck 38 83 _Enderbury_ 37 81 Californian 35 76 _Aves_ 34 74 Fanning Island 34 74 Howland 34 74 _Sidney Island_ 34 74 Mejillones 33 72 Lacepede Island 33 72 _Malden Island_ 32 70 Sombrero 32 70 _Browse Island_ 31 68 _Huon Island_ 28 61 Patos Island 24 52 Jarvis Island 20 44 Cape Vert 11 24 NOTE VI. (p. 314). It may be of interest to refer to a theory put forward by Liebig as to the action of oxalic acid in guano. This, he considered, had the effect of gradually rendering the insoluble calcium phosphate soluble, and giving rise to the formation of ammonium phosphate and calcium oxalate. Such an action would probably take place were the guano allowed to ferment by itself. We know, however, that when it is brought in contact with the soil-particles, all its soluble phosphate is converted into precipitated phosphate. NOTE VII. (p. 326). ANALYSES OF DUNG OF FOWLS, PIGEONS, DUCKS, AND GEESE. (Storer's 'Agricultural Chemistry,' vol. i. p. 367.) Fowls. Pigeons. Ducks. Geese. Water 56.00 52.00 56.60 77.10 Organic matter 25.50 31.00 26.20 13.40 Nitrogen 1.60 1.75 1.00 .55 Phosphoric acid 1.5-2.00 1.5-2.00 1.40 .54 Potash .80-.90 1.0-1.25 .62 .95 Lime 2.00-2.50 1.5-2.00 1.70 .84 Magnesia .75 .50 .35 .20 According to a computation by a Belgian farmer, a pigeon yields about 6 lb. of dung in a year, a hen about 12 lb., a turkey or goose about 25 lb., and a duck 18 lb. CHAPTER IX. NITRATE OF SODA.