# The American Cyclopædia (1879)/Greensand

 The American Cyclopædia Greensand

CONSTITUENTS.   N. J.   France.   Gay Head.   England.

Silica
 46.50 9.00 1.50 8.00 5.00 $\scriptstyle{ \left. \begin{matrix} \ \end{matrix} \right\}\, }$ 21.00 9.00 ....
50.00   56.70   48.50
Potash 10.90  ....  ....
Lime ....  1.62  ....
Alumina 7.00  13.32  17.00
Protoxide of iron 21.00  20.10  22.00
Peroxide of iron
Water 11.00  7.00  7.00
Magnesia ....  1.18  3.80

In New Jersey the greensand (there called marl) is dug from pits during the winter, and brought out upon the fields, where it is spread to be ploughed in. The effect is experienced with the first crop, and continues for several years. — The investigations of Ehrenberg first showed that many of the greensand grains are casts of the microscopic shells of polythalamia (the many-chambered) and of other organic bodies. The shells themselves had disappeared; but the internal form of their cavities was retained in the more durable silicate of iron, which took the place of the animal bodies as these decayed, and preserved their shapes. Even the very finest canals of the cell walls, and all their connecting tubes, are thus petrified and separately exhibited. Many of the grains which cannot be recognized as of this origin still suggest some connection with animal bodies by their forms being sometimes lobed and again presenting the appearance of coprolites. Prof. Bailey by his experiments confirmed the conclusions of Ehrenberg, and, extending his investigations to cretaceous rocks from Alabama and W. Texas, found attached to them grains of greensand exhibiting the same phenomena. From specimens of marl and limestone of the eocene of the southern states he also succeeded in bringing to light similar grains of the same character by dissolving away with dilute acid the calcareous matters. One of his specimens was brought up in sinking the artesian well at Charleston from the depth of 140 ft. The soundings of the coast survey brought up from the depths of the ocean, in the Gulf stream and the gulf of Mexico, something resembling greensand. Count Pourtalès reports one sounding as of this character obtained in lat. 31° 32', lon. 79° 35', at the depth of 150 fathoms. This, as well as the others referred to, were examined by Prof. Bailey, who found them to be greensand, and that this is often in the form of well defined casts of polythalamia, minute mollusks, and branching tubuli. The material he found to be the same as that of the fossil casts; but the chief part of the soundings he found consisted of perfectly preserved shells of the same species, which retained their brilliant colors, and gave evidence by treatment with acid that the soft parts were still present, thus proving the recent existence of the animals. Hence it appears that in some deep seas the production of greensand is still going on, and formations of this obscure material are there growing up by the same agencies which elaborated those of ancient geological periods.