FARMERS' REGISTER— GREEN SAND FORMATION. 



747 



For the Farmers' Register. 



FURTHER OBSERVATIONS ON THE GREEN 

 SAND AND CALCAREOUS MARL. OF VIR- 

 GINIA. 



By Wm. B. Rogers — Professor of Natural Philoso- 

 phy and Chemistry, William and Mary College. 



In a communication published in the 3rtl No. 

 of the Register, I announced the discovery ol" 

 thegreen sand, orsilicate of iron and potash, in the 

 ordinary tertiary marl in Lower Virginia. Geo- 

 logical considerations, taken in connexion with this 

 discover}^, led to tiie intercnce that an older de- 

 positc, consisting in much larger proportion of this 

 peculiar substance, would be found in a region 

 more remote from the seaboard, and not far below 

 the head of tide; and from the great agricultural 

 value of this substance, as proved by the expe- 

 rience of the liirmers in New Jerse\', I was indu- 

 ced to point out its probable position, and to give 

 Buch hints and directions with regard to its accom- 

 panying indications as might prove useful in any 

 researches which might be undertaken by persons 

 residing in the region in which it was supposed to 

 exist. Since the publication of the paper referred 

 to, as far as other engagements would permit, this 

 important inquiry has been actively continued, not 

 only in reference to the presumed deposite above 

 mentioned, but also to the extensive calcareous 

 formation of our lower counties. 



Besides the practical importance of this investi- 

 gation to the agriculture of a large district of the 

 state, in a purely geological aspect, it was calcula- 

 ted to excite the highest interest. In the vast re- 

 gion of our tide-water country, at farthest, only 

 two members of the tertiary group of forma- 

 tions liad been hitherto discovered, and no decided 

 indications of a secondary deposite likely to prove 

 interesting to men of science, had been found. 

 At the mouth of the Potomac, and at some other 

 points, a deposite had been detected by Mr. Con- 

 rad of Philadelphia, which from the great pre- 

 dominance of shells of existing species, was re- 

 garded by him as belonging to the upper or newer 

 tertiary, and as analogous to the Crag of Eng- 

 land. The same eminent conchologist by an ex- 

 amination of numerous fossils Irom York town, 

 Sutiolk, the James River, near Smithfield, and 

 other localities, had clearly proved that this por- 

 tion of the tertiary series was of greater antiquity 

 than the former, and accordingly he has recently 

 applied to it the title of middle tertiary — which, 

 as some geologists in Europe divide the tertiary 

 group into four period*, would include both the 

 second and third of these subordinate formations. 

 The lower tertiary, which Mr. Conrad had so 

 successfully investigated in Alabama, had not as 

 yet been brought to light w^ithin the limits of Vir- 

 ginia. Thius, therefore, these inquiries appeared 

 fraught with the lively interest of scientific discov- 

 ery, while at the same time they inspired the ani- 

 mating hope, that in some of their results, they 

 might eventually be found conducive to the inter- 

 ests of an important district of the slate. 



From the great extent of the middle tertiary 

 of Lower Virginia, it was to be expected that, 

 notwithstanding the diligence and learning of those 

 who had visited several ol its interesting localities, 

 with the view of studying its fossil contents, an ex- 

 tensive field of future discovery would be opened 



to the scientific explorer — and a great variety o^^ 

 new and peculiar fiissils would be Drought to light. 

 To a certain extent this anticipation has been re- 

 alized; and the occasional examinations which I 

 have made in this vicinity, and at some remote 

 points, have been rewarded by an extension of the 

 list of fossils, and the discovery of a number of 

 new and interesting species. To the readers of 

 the Register, generally, the details of these ob- 

 servations would appear unimportant, if not use- 

 less, and must therefore be omitted. At the same 

 time, I may be allowed to add, that such liicts are 

 frequently invested with a. practical interest, V)y the 

 aids which they furnish to other and more impor- 

 tant discoveries; and that, however little ^■alue, in 

 the abstract, would attach to an enumeration and 

 description of the shells, zoophytes and other re- 

 mains of our marl banks, they are absolutely es- 

 sential in studying the physical hi.story of this por- 

 tion of the globe, and may prove of some assist- 

 ance not only in guiding the researches of the 

 farmer after mari, but in directing his choice of cal- 

 careous manure when various deposites of this 

 substance are offered for his selection. Of the 

 latter point, several striking illustrations might be 

 adduced — but I shall content myself^_ fi)r the pre- 

 sent, with the statement of a single fact. A small 

 shell of rough exterior, and rather irregular form, 

 a species of chama, is frequently found in very 

 extensive beds in this vicinity and at other points, 

 forming nearly the entire calcareous portion of the 

 deposite. From its pecuhar form and friable 

 character, it is most generally in a condition to be 

 eminently serviceable as a manure. As the strata 

 both above and below are often of a very differ- 

 ent texture, though perhaps nearly equal to it in 

 regard to their calcareous contents, a choice is at 

 once presented to the farmer, in which, he wi'l be 

 guided even more by the nature of the shell em- 

 bedded, than by the comparative abundance of 

 carbonate of lime. But so little attention has been 

 paid to the characters of the fossils contained in 

 our mari-banks, that even in places where the 

 manure has been longest and most successfully in 

 use, a less valuable stratum is soinetimes selected 

 in preference to one of superior fertilizing power. 

 A more minute observation of such particulars, 

 can scarcely be expected in the absence of some 

 popular guide, in the (brm of delineations and de- 

 scriptions of the more prominent shells, exempted 

 as much as possible fiom technical or nierely 

 scientific phraseology. Some such illustrations 

 may hereafter be fijrnished in a cheap form in the 

 progress of a geological examination of the east- 

 ern region of our state. 



Since the publication of my former paper, a 

 great number of additional observations have been 

 made with regard to the green sand contained in 

 our ordinary middle tertiary mari. Its uniform 

 presence in this deposite, in a greater or less pro- 

 portion, seem.s' now to be sufficiently established. 

 That it is generally present insufllcient quantity 

 to enhance in any important degree the agricultu- 

 ral utility of the manure, it would be going much 

 too tar to assert; but that in many cases the propor- 

 tion is such as cannot fail of producing liighly 

 beneficial effects upon vegetation, would seem to 

 be demonstrated not only by the long experience 

 of the farmers of New Jersey with the green sand 

 itself, but by the observations of individuals 

 amongst ourselves who have been in the habit of 



