Farm-yard manure is a mixture of the dung and urine of domestic animals, with the straw used as litter; and its value and composition must necessarily depend upon that of these substances, as well as on the proportion in which they are mixed. The dung of animals consists of that part of their food which passes through the intestinal canal without undergoing assimilation; the urine containing the portion which has been assimilated and is again excreted, in consequence of the changes which are proceeding in the tissues of the animal. Their composition is naturally very different, and must be separately considered. _Urine._--Urine consists of a variety of earthy and alkaline salts, and of certain organic substances, generally rich in nitrogen, dissolved in a large quantity of water. That of the different domestic animals has been frequently examined, but the analyses of Fromberg give the most complete view of their manurial value:-- Horse. Swine. Ox. Goat. Sheep. Extractive matter } 2.132 0.142 2.248 0.100 0.340 soluble in water } Extractive matter } 2.550 0.387 1.421 0.454 3.330 soluble in spirit} Salts soluble in } 2.340 0.909 2.442 0.850 1.957 water } Salts insoluble in} 1.880 0.088 0.155 0.080 0.052 water } Urea 1.244 0.273 1.976 0.378 1.262 Hippuric acid 1.260 ... 0.550 0.125 ... Mucus 0.005 0.005 0.007 0.006 0.025 Water 88.589 98.196 91.201 98.007 92.897 ------ ------- ------- ------- ------- 100.000 100.000 100.000 100.000 99.863 _Composition of the Ash of these Urines._ Horse. Swine. Ox. Goat. Sheep. Carbonate of lime 12.50 ... 1.07 trace 0.82 Carbonate of magnesia 9.46 ... 6.93 7.3 0.46 Carbonate of potash 46.09 12.10 77.28 trace ... Carbonate of soda 10.33 ... ... 53.0 42.25 Sulphate of potash ... ... 13.30 ... 2.98 Sulphate of soda 13.04 7.00 ... 25.0 7.72 Phosphate of soda ... 19.00 ... ... ... Phosphate of lime } Phosphate of magnesia } ... 8.80 ... ... 0.70 Chloride of sodium 6.94 53.10 0.30 14.7 32.01 Chloride of potassium ... trace ... ... 12.00 Silica 0.55 ... 0.35 ... 1.06 Oxide of iron and loss 1.09 ... 0.77 ... ... ------ ------ ------ ------ ------ 100.00 100.00 100.00 100.00 100.00 Human urine has been accurately examined by Berzelius, although his estimate of the proportion of urea is generally admitted to be above the average. His analysis gives the following numbers:--