MANURES. 57 



gists have regarded it, the green-sand is in fact a compound, which fluctuates 

 widely in its external characters and in its chemical composition. 



Though it is not presumed that among those engaged in agriculture, more 

 than a very few persons possess the requisite chemical skill, or the facilities 

 for this species of research; yet, for the sake of enabling those to execute it, 

 who may chance to be competent to this kind of analysis, I have thought it 

 well to introduce a statement of my method of analyzing the mineral in ques- 

 tion. Several plans, modifications of the same general method, have been tried 

 for the purpose of arriving, if possible, at some mode sufficiently simple to 

 make it practicable by those who possess but a limited knowledge of chemistry. 

 But the nature of the compound seems not to admit of either a very direct or 

 expeditious course of operation, and though practice has taught me the steps 

 which are the most certain and least operose in the case, I can hardly hope, 

 that the analysis of the green marl can at present be brought within the skill 

 of such as are not already professionally familiar with this laborious and intri- 

 cate art. 



Method of Analyzing the Green-sand. (a) Digest the mass in a flask of pretty 

 strong muriatic acid, "by a sand-bath heat for at least three days, or boil it ac- 

 tively for five or six hours. Everything is dissolved but the silica, which must 

 be filtered, ignited, and weighed. (6) Precipitate \heoxiile of iron and alumina 

 by ammonia and estimate them together, or detach the alumina by a/itst ic 

 potash, (c) Evaporate the ammoniacal solution to total dryiR'ss. and heat the 

 mass to incipient redness, to expel the muriate of ammonia. There remain 

 the chlorides of calcium, magnesium, and potassium, which redissolve in 

 water, dividing the liquor. (</) To one half add oxalate of ammonia, and 

 separate the lime, then by ammonia and phosphate of soda separate the mag- 

 nesia. Subtract the combined weight of these two computed as chlorides from 

 the original triple chloride, and we have the chloride of potassium, (e) Now 

 evaporate the other half again to dryness and dissolve up all the chlorides of 

 calcium and magnesium bv alcohol, and dry and weigh the residual chloride 

 of potassium. If further check is necessary, convert this into chloroplatinate 

 of potassium and estimate the potash from this. 



Mr. PIERCE, in a Survey of the Alluvial District of New 

 Jersey, furnished for SILLIMAN'S Journal, thus describes the 

 use and effects of marl: 



"I visited many beds of marl, and found them of a pretty 

 uniform character. The colour is generally grey or greyish- 

 white, and good in proportion to its whiteness, which indicates 

 the quantity of calcareous earth it contains. From thirty to 

 eighty loads of marl are spread upon an acre. It is believed 

 that a good dressing will last from twelve to twenty years. 

 The lands of Monmouth county alone are said to be enhanced 

 in value more than half a million of dollars by the discovery 

 and use of marl. 



"A respectable farmer of Middletown mentioned to me that 

 a few years since he contemplated abandoning his large farm 

 for land in other districts, as his own was unproductive. Learn- 

 ing the discovery of marl, he made himself acquainted with 

 the mode of examining, and found good beds of this manure in 

 almost every field, and liberally applied dressings to the soil. In 

 walking over his ground, I observed rich white marl breaking 

 out of banks and hillocks, and the streams paved with marine 

 decaying shells. For more than a century this land had been, 

 regarded by the proprietors as worn out and useless. 



