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posits. It is very soft, sparingly mixed with globular grains, ail yields a high amount of phosphate of lime with some magnesia phosphate. As it contains perceptible traces of nitrogenous organic matter, it seems to be of animal origin, similar to that of Mexican Guano. A sample representing a pile of twenty tons, collected in a cave of about 10' length, which I visited myself, shows almost 50 per cent. of lime-phosphate, thus proving it to be a valuable article worthy of consideration.
The lower that land, which is by far the largest of the two, covering scarcely less than two thousand acres, is the great depot to which I wish to call your attention.
Being accessible with but little outlay of capital, and furnishing at a low calculation one thousand tons to the acre, it will constitute, independent of the rocky phosphate, for a grout number of years the main source of supply for the trade.
This deposit, the product of disintegration of the richer layers, has the same globular formation, but the globules are larger, the coating is thinner and consists of alumina with some silicates. It is of light brown color and analyses from 62 to 72 per cent. of phosphate of lime, and will be a desirable material for the manufacturer.
From the peculiar formation, and the presence of free exile of iron, it is fair to suppose that the phosphate of lime of the Navassa Island, originated from phosphate of iron and alumina, which alternating with strata of limestone, were gradually transformed into phosphate of lime. This supposition is corroborated by the large quantity of oxide of iron which is found in many places of the island, and had been set free during the process of transformation by the lime of the limestone.
I have to express here the regret, that during my exploration of the island, I did not find any crystals of this phosphate, as from my analysis I am strongly inclined to consider it a new mineral, which I should propose to call "Navassite," if my suppositions were confirmed by subsequent examinations of the chemical and crystallographic characters of more perfect specimens.
But if I have to leave for the present this question of scientific interest without solution, I am happy to record here the discovery, I may say, of an inexhaustible quantity of a mineral substance, the phosphate of lime, so instrumental in the development of agricultural wealth.
