Abstract
“PRACTICE with Science” is the title of a volume of essays (the second of a series), issuing from the Royal Agricultural College, Cirencester, and containing contributions from the members of the staff of that institution. Amongst other papers is an interesting account by Prof. Thiselton Dyer of the geological distribution of Tricalcic Phosphate; that is to say, a sketch of the chief sources of mineral phosphate of lime, whether as apatite, osteolite, phosphatite, coprolite, or guano. Mr. Dyer points out the abundance of phosphate of lime in igneous rocks, but hesitates about tracing its origin in such beds either to direct chemical combination, or to the inclusion of organically-formed phosphate in the rocks in question. He does not, in short, discuss the possibility of the combination of phosphoric acid and lime in the primæval state of the globe without the intervention of life, which one distinguished geologist at least denies. Mr. Dyer traces the occurrence of tricalcic phosphate in the various sedimentary deposits with great care, having obviously taken much trouble to render his statement an exhaustive one. He considers the many structureless masses of phosphatic deposits which occur “as residuary evidence of formerly existing life, of which they are to some extent the measure,” as graphite is in other cases. A greater influence in the production of these masses is attributed to animal than to vegetal life, though marine plants are stated to be especially rich in phosphate of lime, and have undoubtedly played their part in its introduction into sedimentary strata. Mr. Dyer mentions that the recent Brachiopod Lingula has 86 per cent, of phosphate of lime in the mineral ingredients of its shell; and the occurrence of large quantities of phosphate of lime in the great Laurentian and Silurian formations is noticed by him in detail, as well as its occurrence in Devonian and Carboniferous limestones. In emerging to the group of mesozoic strata, we leave behind almost entirely those veins and beds of “phosphate” which occur in the older and more changed rocks, where the segregation of the phosphate of lime has been more completely effected, owing to the greater age of the beds. In mesozoic and tertiary strata we find those nodules which have so erroneously been confused with “coprolites”—the droppings of fish, which are not unfrequently preserved in the fine sediment of the Liassic and the Rhætic beds of the chalk—though beds of flaggy phosphate also occur in some deposits of this age.
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LANKESTER, E. The Sources of Phosphatic Manures . Nature 3, 62–63 (1870). https://doi.org/10.1038/003062a0
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DOI: https://doi.org/10.1038/003062a0