It is important, before beginning an analysis, to know the origin of the substances to be determined. As has already been pointed out in volume first the process which would be accurate with a substance of a mineral origin might lead to error if applied to the same element in organic combination. This is particularly true of phosphorus and potash. A simple microscopic examination will usually enable the analyst to determine the nature of the sample. In this manner, in the case of a phosphate, it would at once be determined whether it was bone, mineral, or basic slag. The odor, color, and general consistence will also aid in the determination. =4. Valuation of Fertilizing Ingredients.=—Perhaps there are no more numerous and perplexing questions propounded to the analyst than those which relate to the value of fertilizing materials. There is none harder to answer. As a rule these questions are asked by the farmer, and refer to the fertilizers put down on his fields. In such cases the cost of transportation is an important factor in the answer. The farther the farmer is removed from the place of fertilizer manufacture the greater, as a rule, will be the cost. Whether the transportation is over land or by water also plays an important part in the final cost. The discovery of new stores of fertilizing materials has also much to do with the price. This fact is especially noticeable in this country, where the price of crude phosphates at the mines has fallen in a few years from nearly six dollars to three dollars and forty-three cents per ton[1]. This decrease has been largely due to discoveries of vast beds of phosphatic deposits in Florida, North Carolina, Tennessee, and Virginia. The state of trade, magnitude of crops, and the vigor of commerce also affect, in a marked degree, the cost of the raw materials of commercial fertilizers. =5. Trade Values of Fertilizing Ingredients in Raw Materials and Chemicals.=—The values proposed by the Massachusetts Experiment Station are given below.[2] Cents per pound. Nitrogen in ammonia salts, 19 “ “ nitrates, 14½ Organic nitrogen in dry and fine-ground fish, meat, blood, and in high-grade mixed fertilizers, 18½ “ “ “ cottonseed meal, linseed meal, and castor pomace, 15 “ “ “ fine-ground bone and tankage, 16½ “ “ “ fine-ground medium bone and tankage, 15 “ “ “ medium bone and tankage, 12 “ “ “ coarse bone and tankage, 7 “ “ “ hair, horn shavings, and coarse fish scraps, 7