AGRICULTURAL TEXT-BOOK. 331 



mills ; but is supposed to differ in quality, some mines having 

 a higher reputation than others, probably in consequence of 

 greater purity. That used by masons is said to be ground from 

 selected specimens. 



It were interesting to try qtick lime along side of plaster, so as to as 

 certain the relative effect and profit of eacb. At present, plaster in 

 Michigan is expensive, costing $7.00 loose or $9.00 in barrels per ton 

 at the mill ; and most that is used is carried by land either from De 

 troit or Grand Rapids ; while there are few farms in the interior of 

 the St;ite which cannot procure excellent marl at little more expense 

 than digging. The late Dr. Houghton expressed the opinion that upon 

 our s;mdy lands, the shell marls, even without burning, would prove 

 quite as effective. Of the quantity consumed in this State we have no 

 correct statistics. We find that during the year ending June 1853, the 

 Central Railroad carried 2,613 tons ; and allowing as much more for the 

 Southern Railroad, and for private conveyance, we have a total of 5226 

 tons averaging $10 per ton delivered on the farm, which makes a total 

 of $52,260 per annum for this one manure. It is very important that our 

 ranrls and peats should be more fully investigated and their effects care 

 fully tried. 



Prof. Johnston states that when mixed with common salt, the 

 action of gypsum upon clovers, beans, peas, &amp;lt;fec., appears to be 

 greatly increased. 



W. Alexander, of Ballochmyle, Scotland, dressed an apparently worth 

 iest crop of young beans with a mixture of 2 cwt. of gypsum, and one of 

 common salt per acre. The effect was almost marvelous, and instead 

 of a bad crop, his beans were the admiration of the country. He found 

 a sensible effect produced by this mixture even after the beans were in 

 flower. 



Plaster acts as a stimulant, and its tendency is to impoverish 

 the soil unless organic and other manures are liberally added. 



705. MARL properly means an earthy mixture containing not 

 less than 20 per cent of carbonate of lime. If the proportion of 

 lime be less than this, the mixture is rather a marly clay, con 

 taining potash or silica in place of lime, as in the Green-sand 

 marls of New Jersey, and Silicious marls of Massachusetts. (See 



