THE FARMERS' REGISTER. 



271 



(B.)—Mar\ 9 parts, clay 1, combined with half' 

 its bulk of saiul, rel'used lo liariien under wa- 

 ter, but when exi>osed to ibtt atinospliere be- 

 came compact and hard, but was slightly acted 

 upon by water alter several months' exposure 

 to its action. 



(C.)— JNlarl 7 parts, clay 1, combined with half 

 its bulk of sand, refused lo harden under water, 

 but alter exposure to the atmosphere became 

 so hard and copipact as to perfectly resist the 

 action of water, though covered by it lor 

 months. 



Mortars Ji and C would not answer as hy- 

 draulic cements in masonry exposed immediately 

 after iis completion to the action of water, but 

 would form an admirable stucco, and would sub- 

 serve all tlie purposes of a hydraulic cement, 

 where the masonry was permitted to harden in 

 the air belbre beinir exposed to the action of wa- 

 ter, as in dry docks, the locks and viaducts of 

 canals, &c. These experiments satislactorily show 

 the capacity of the clays of Virginia to forn) hy- 

 draulic cement, when mixed with lime in certain 

 proportions. It is by no means intended to con- 

 vey the impression that the relative proportions ot 

 the materials selected in the above experiments 

 are those best calculated to form a good cement. 

 Doubtless liirther examination would have given 

 better proportions, but it was considered unneces- 

 sary to multiply experiments upon the subject; 

 lor however accurately the proportions might have 

 been determined lor the materials used, they would 

 only have been applicable to clays identical in 

 composition with the one used. As the clays are 

 very variable in composition, experiment in each 

 instance can alone determine the proper propor- 

 tions and afford a guide to the mixture of the ma- 

 terials. Experiments similar to those above de- 

 scribed will enable any individual to select the 

 proportions best calculated to -secure success. Vi- 

 cai, whose extensive experience as an engineer 

 entitles his opinion to great credit, recommends 

 the Ibllowing proportions : 20 parts of dry clay, to 

 SO parts of unslaked lime, or 110 parts of slaked 

 lime; if the lime be unburned 140 parts should be 

 used with 20 parts of clay. Messrs. Brian and 

 Saint Leger at their manuliactory at Meudon, pur- 

 sue the following process: the clay and chalk 

 (uncalcined) in the proportion of one measure of 

 the former to four of the latter, are Ibrmed into a 

 pulp with water, to effect their more perfect inter- 

 mixture ; further to promote, which the pulp is 

 thoroughly stirred. The watery portion of the 

 pulp is then separated from the solid, and the lat- 

 ter is moulded into small prisms, which after dry- 

 ing are ready for the -market, the necessary burn- 

 ing being done by the purchaser previous to using 

 the cement. In this manner is formed an artificial 

 cement, possessing all the properties ol the natu- 

 ral hydraulic cement, as has been satislactorily 

 proved in the construction of the masonry of the 

 harbor of Toulon, the canals of St. Martin and 

 St. Maur, and other public works, in which the 

 artificial cement has been exclusively used.* This 



* The process pursued at Meudon could be applied 

 without alteration to the white chalky marl which oc- 

 curs in the northern part of the state. This marl is 

 perfectly free from shells or fragments of shells, and 

 occurs in a pulverulent powder, or friable nodules. 

 This variety of marl is largely developed in the county 



process cannot be strictly applied lo I he clay and 

 rock-marl, as the latter cannot be sulliciently pul- 

 verized to form the necessary admixture with the 

 clay, without being first burned. After havinc 

 determined by experiment the relative profiorMoiis 

 of the ingredients, the clay should he thoroughly 

 mixed by any convenient method with the lime, 

 derived from ihe calcination of the rock marl, or 

 other source, and the mixture subjected to a heat 

 as intense as that usually employed in burning 

 lime, when the cement will be ready lor use. The 

 lime of the rock-marl was not used in these expe- 

 riments li"om any supposed superiority over that 

 derived from any other source, but merely to show 

 how successfully it can be substituted lor the lime 

 of commerce. A band of this variety of marl 

 extends-«long the eastern margin of the marl re- 

 gion, fiom the northern to the southern boundary 

 of the state. Several specimens of this marl, se- 

 lected li'om localities widely separated, averaged 

 81 per cent, of carbonate of lime, while it not un- 

 liequently, as in the vicinity of Smithfield, con- 

 tains over 90 percent, of ihis ingredient. The 

 average richness of the rock-marl in lime is equal 

 to that of the limestone used in this state and 

 Pennsylvania for burning lime; yet to this pur- 

 pose it has rarely been applied, though admirably 

 adapted for it. by its richness, its open porous tex- 

 ture, which causes it to yield more readily to heat 

 than a compact limestone, and its extensive dis- 

 tribution in a manner presenting great facilities for 

 quarrying. In urging this neglected, though use- 

 ful substance, upon the attention of the public, re- 

 gard has only been paid to its applicability to 

 mortars and cements, it is unnecessary to say that 

 it has equally strong claims upon the attention of 

 those agriculturists who acknowledge the benefi- 

 cial efficacy of lime in their prolession. Were it 

 not lor the daily proofs to the contrary, it would be 

 incredible that ^ny should still be skeptical as to 

 the efficacy of a substance whose value as an 

 asricultural agent was admitted in the days of 

 Pliny, whose use has been sanctioned by the en- 

 lightened agriculturists of Europe lor years, and ' 

 to which large portions of our own country are in- 

 debted for their regeneration from a condition of 

 poverty and sterility. Nature adds her confirming 

 testimony to that of man, as the richest soils, ccs- 

 teris paribus, are those derived from the decom- 

 position of calcareous rocks. The superior rich- 

 ness of soils derived from calcareous rocks is 

 strikingly exhibited in the Knobby and other moun- 

 tains of Virginia, the summits of which consist of 

 limestone, but whose sides are flanked with sand- 

 stone. The height to which the sandstone as- 

 cends on the side of the mountain, and the bound- 

 ary between it and the limestone, can be seen at 

 the distance of miles, being strongly marked by 

 the rich luxuriant vegetation of the latter, and the 

 scattering stinted vegetation of the former. Not 

 unfrequently a rivulet rising in the lime-stone con- 

 veys calcareous matter to the soil of the sand- 

 stone, thus forming a fertile belt of land in the 

 midst of sterility, and affbrding a demonstration of 

 the fenilizing power of lime, and a happy illus- 

 tration of the manner in which nature causes the 

 superabundance of one soil to contribute to the 

 poverty of another. Asmodeus informed Don 



of Middlesex, near Urbanna, where it contains from 

 69 to 78 per cent, of carbonate of lime. 



