270 



THE FARMERS' REGISTER. 



interests of farmers ought to lend some aid in 

 solving it. All the varieties of grease, tar, and 

 their combinations have been resorted to; and 

 there are other substances wliich have of iatler 

 years been adopted to lessen the friction ol ma- 

 chinery ; sucli as black-lead and soap-stone pul- 

 verized, and mixed with small quantities of fat of 

 some kind. Yet [ have seen no results of com- 

 paraiive experiments published to instruct and 

 guide th.e public. Should any of the readers of 

 the Cabinet possess practical knowledge on this 

 useful and interesting subject, they would much 

 oblige some of your readers by making it public 

 Ihro'ugh yo'jr columns. We have many anti''s in 

 our vvidely extended country, but we want one 

 more, in the lorm of an anti-friction composition, 

 lijr application to cart and wagon-wheels, lo make 

 them revolve with less labor to our horses ; and 

 he who will discover and make it known through 

 the Cabinet, will deserve weil of the community 

 at large. ^• 



CAPACITY OF THE CLAYS A^D UOCK-MARL OP 

 VIRGINIA, TO FORM HYDRAULIC CEMENT, 

 AND THE APPLICABILITY-^ OF ROCK-MARL 

 TO BURNING LIME. 



To the Editor of tlie l'"aimeis' Ilegister. 



Presuming that a new and usel'ul application of 

 substances so generally and widely diti'used as 

 the clays and marls of Virginia, will be both in- 

 teresting to yourself and acceptable to your read- 

 ers, I send you the results of some experiments 

 made upon them in reference to their capacity lor 

 forming artificial hydraulic cements. Learning 

 through the work of "Vicai* of the successlul appli- 

 cation' by the French engineers of the clays and 

 chalk ol 'France to the manulacture of hydraulic 

 cement, I was induced to ascertain how liir their 

 generalizations were applicable to the clays and 

 rock-marl of Virginia, which I was aware resem- 

 bled in composition the chalk and clay of France. 

 The clay used in these experiments was of the 

 variety liimiliarly known as pipe clay or fuller's 

 earth, which, from its absorbent power, is so fre- 

 quently used in domestic economy for removing 

 grease. The clays best adapted to making hy- 

 draulic cement are free from grit or coarse sand, 

 are fine grained and homogeneous, have an unc- 

 tuous feeling, and are rich in alumina.f The ap- 

 pearance of a clay is a very imperfect criterion of 

 the amount of silica or sand it contains, as clays 

 are frequently rich in silica, whose external ap- 

 pearance would not indicate its presence. The 

 existence of silica, however, in that minutely di- 

 vided state in whichit is perceptible neither to the 

 eight nor touch, is by no means an unfavorable in- 

 gredient, as it is in that condition most favorable 

 to its.combining with the lime, and forming with 

 it a silicate, which is probably essential to the har- 

 dening of tlie cement. Clays possessing the re- 



* Vicat on Cements, translated by Capt. Smith, 

 London, 1837. 



t Alumina is mentioned as one of the requisite in- 

 gredients of the clay, more from deference for the opi- 

 nions of others, than from any convictions of my own. 

 I do not regard the presence of alumina necessary, 

 and am inclined to refer the hardening of the cement 

 to the formation of a silicate. 



quisiie- qualities chiefly abound in the marl region 

 of Virginia, but are by no means rare liirlher 

 west; und, wherever found, will, if mixed in the 

 proper proportion with lime, lorm a hydraulic ce- 

 ment. 'J'he clay of Vaugirard, used in the manu- 

 facture of artificial hydraulic cement, at Meudon, 

 near Paris, consists of 



Silica 63 



Alumina 28 



Oxide of iron 7 



Loss 2 



100 



The resemblance in composition of the clays of 

 Virginia to that so successfully used at Meudon, 

 will be seen from the following analyses. 



(^^.) — Clay from Smithfield. 



Silica . - . _ 68.4 



Alumina tinged with prot-oxide of iron 24.7 



Water* and loss - . . 6.9 



100.0 



(B.) — Clay from ScotVs factory, 4 m,iles from 



Smithfield. 



Silica - - . - 74.4 



Alumina tinged with prot-oxide of iron 17.8 



Water* and loss . . - 7.8 



100.0 



Clay (i?) was used in the experiments quoted 

 below. This clay was of a dingy drab color, 

 compact, fine-grained, homogeneous and sapona- 

 ceous. 



The rock-marl was from the estate of Mr. M. 

 T. Dickson, in the vicinity of Smithfield ; it con- 

 sisted of small frajiments of shells, cemented to- 

 gether. This marl was found upon analysis to 

 contain 95.9 per cent, of carbonate of lime, the 

 remainder consisting of ochreous sand. The marl 

 and clay previously pulverized were mixed in 

 the proportions stated below ; iRe mixture waa 

 then heated sufficiently to render the lime caustic, 

 or to convert it into quick-lime. After burning, 

 the mixture was formed into a mortar by adding 

 water and sand, as in the ordinary process. Mor- 

 tars formed in this manner, of different propor- 

 tions of the ingredient, were spread on the bot- 

 toins of China jars to the depth of an inch, and 

 the jars filled with water. The different propor- 

 fions of the ingredients used in the mortars, and 

 their respective behavior when exposed to the ac- 

 tion of water, is stated below. 



(jf.)'\ — Mar! 9 parts, clay 1, combined with one- 

 fourth its bulk of sand, rapidly hardened under 

 water, forming a compact mass, perfectly re- 

 sisting the action of the water, and may be 

 considered a hydraulic cement of the best 

 quality. 



* It was considered unnecessary to determine the 

 exact amount of water in the clays analyzed., as it had 

 no connexion with the result. The whole amount 

 quoted as " water and loss" in the analysis consists 

 chiefly of water, as the loss is but the fractional part 

 of a grain. 



t These experiments were made in the winter of 

 1839 and '40 ; and henre the results have been fully 

 tested. 



