FARMERS' REGISTER— DISCOVERY OF MARL. 



425 



plied the familiar saying which implies that the 

 o;reatest folly is attended by the best fortune — but 

 this is in no wise applicable to him, especially in 

 farming; operations. Some useful hints may be 

 gathered, and many curious speculations drawn 

 from the aliove facts ; but as paper and time are 

 nearly exhausted, I leave them to abler hands, and 

 will close with the expression of thanks for the 

 pleasure received and the profit hoped to be deri- 

 ved from the spirited " Farmers' Register." 

 Respectfully, 



THOMAS MEAUX. 



MAGKESIAN MARL. 



The earth described in the foregoing letter deserves 

 more than common attention, not only on account of its 

 peculiar appearance, and its being found in a region 

 before supposed destitute of calcareous earth, but also 

 for its singular chemical constitution. To the eye, it 

 does not seem to be even slightly calcareous — oral best, 

 to be an argillaceous marl, very poor in calcareous mat- 

 ter. But upon examination by proper tests, it was 

 found to be richer in earthy carbonates than any whole 

 body of marl yet known in Virginia. By the most com- 

 mon mode of analysis, (separating the clay and sand, 

 and estimating the calcareous earth by subtracting the 

 cpianlities fovmd from the whole specimen,) and also by 

 the most correct mode, with all marls before examined, 

 (measuring the gas evolved,) the whole of the earthy 

 carbonates would have passed for so much Calcareous 

 earth, and the, marl would have been reported as con- 

 taining 85 in the 100 parts of that ingredient. But this 

 astonishing result, and the consequent importance of 

 the discovery, induced -varied and more extended ex- 

 periments to be made, which served to. prove that the 

 earth contained a large proportion of carbonate of magne- 

 sia, in addition to as much carbonate of lime, as would 

 alone constitute a rich manure. Whether the addition 

 of the magnesia increases or lessens the value of the 

 whole as manure, will not now be considered. It is, 

 however, iinportant that it should be knoWn as consti- 

 tuting so large a proportion of this earth, especially as 

 it will probably be found in many other places neartlie 

 granite range. The effervescence of this marl, even 

 when finely pounded and exposed to the action of 

 strong acids, is remarkably slow for its strength — much 

 slower than that of common marl of the poorest kind. 

 This peculiarity first caused the suspicion to be formed 

 that magnesia was present ; and the same circumstance 

 may serve to guide to the like result, in future discove- 

 ries of similar magnesian marls. 



The first lump of this earth which was examined, 

 Was received from Mr. Steger, and analyzed, before Dr. 

 Mcaux's letter was brought with another sample. The 

 chemical character of both was very nearly the same, 

 but there was some difference in the appearance of the 

 two. The first seemed to be composed of very thin la- 

 mince, the lines between which were quite plain to the 

 eye, but all still forming a perfectly solid mass. In the 

 second mass no lamince, nor lines were seen— but some 

 scattered black particles, too small to be separated for 

 trial, which looked like the specks of charcoal. When 

 moist, llie earth is of an ash color — when dry, a very 

 light ash, or dirty white. The dry lumps seems to be 

 about as hard as chalk, and break much in the same 



Vol. I.— 54 



manner. When lumps are thrown into a glass of wa- 

 ter and left undisturbed, some retain their form, but 

 others crumble rapidly, and fall to what might be dalb 

 ed powder, if that term could be properly applied to a 

 substance covered by water. The small lumps which 

 were not thus reduced, were mostly tiiiged on one side 

 with the color of rust of iron, which probably marks the 

 exposed surface of the bank. It seems likely that not- 

 withstanding the hardness of the marl, it will be easily 

 made fine enough by exposure to rain and freezing, 

 when used as manure. The constituent parts will now 

 be stated. 



100 grains of the first sample, yielded a bulk of car- 

 bonic gas equal to 43 oz. measures of water, which 

 would indicate 86 grains of carbonate of lime (or calca- 

 reous earth) to have been dissolved by the acid applied, 

 if all the earthy carbonate had been of lime, and none 

 of magnesia. The amount of both these earths was 

 nearly that quantity (8G grains) but not exactly, as 

 magnesia combines with proportions of carbonic acid 

 different from lime, 



16 grains of dark ash colored clay, without a parti- 

 cle of sand, was all the solid matter remaining. 

 Of the second specimen, 



100 grains evolved 42^ measures of carbonic acid gasy 

 indicating 85 grains of earthy carbonates, widiout al- 

 lowing for the error above referred to, caused by part 

 being magnesia. 



The soluble parts were then separated from the solid, 

 and the lime from the magnesia, by the processes di- 

 rected by Davy, and the proportions found to be as fol- 

 lows : 



13 grains of dark clay apparently free from all .sili- 



cious matter, 



50 — — carbonate of lime. 



31 — — carbonate of magnesia, 



94 



6 loss', 



100 



The loss was caused by some of the earth's being una- 

 voidably left adhering to the several filtering papers, 

 in which manner all the different parts were collected 

 separately, and weighed after being scraped off. 



Besides these different modes of examination, (one of 

 which served to give the proportion of carbonic acid, 

 and the other of each of the three earthy ingredients,) 

 there were several other methods tried, more or less 

 complete, but all of which tended to the same general 

 results. Indeed, the want of proper apparatus, and of 

 some of the most convenient tests, as well as the inex- 

 perience and unskilfidness of the operator, made it ne- 

 cessary to employ much time and trouble in repeated 

 and varied experiments, which were thought due to the 

 importance of the subject. But however slowly and 

 awkwardly the results may have been reached, they are 

 not the less relied on as being correct — or enough so for 

 every useful purpose. Among other variations of the 

 mode of examination, one was to add slowly to the pul- 

 verized marl, sulphuric acid, grinding them well together 

 (in a semi-fluid state,) in a glass vessel. After being 

 thus well mixed, and remaining some hours, enough wa- 

 ter was added to enable the soluble parts to be separated 



