332 AGRICULTURAL TEXT-BOOK. 



117, 118, 119, 120, p. 37 J Of the true marls, there are 

 many varieties, differing both in composition and external char 

 acter ; and consequently in value. 



The following are analyses of marls in Seneca Co., N. Y. 



No. 1, No. 2, No. 3. 



Moisture, - - 4.50 1.0 3.48 



Organic matter, - 8.50 4.20 1.65 



Insoluble sand, - 6.60 6.0 5.0 



Carbonate of lime, - 77.10 83.33 83.35 



Magnesia, - - 2.10 2.16 40 



Phosphoric acid.) , on 086 



Alumina, \ 21)0 



Common Salt, 0.20 



Sulphate of lime, 50 



Sulphuric acid, - 0.46 



The lime marls appear to be formed in two modes ; (a,) by 

 the deposite of lime brought to the surface by springs ; (b t ) by 

 the accumulation of shells, and minute forms of animal life, or 

 Infusoria, often microscopic, with calcareous coverings. &quot; Some 

 of these are so minute, that a cubic inch of stone has been cal 

 culated to contain the remains of 41 thousand millions of them 

 and yet deposites composed almost entirely of such remains 

 have been met with of 20 and 30 feet in thickness. How very 

 striking is it to find the united labors of these invisible creatures 

 capable of producing such extraordinary effects ! How very lit 

 tle we really know of what is going on around us !&quot; (Johnston.) 



The marls of Michigan are believed to consist of both these 

 kinds, but especially of the latter. We believe they have nev 

 er yet been analyzed, but will probably be found rich in phos 

 phoric acid and ammonia. Mr. Del afield states of the New 

 York marls above mentioned, that the poorest will afford 25 Ibs 

 of phosphoric acid to every ton of dry and weathered marl. 

 This is equal to 45 Ibs of phosphate of lime, a quantity found in 

 80 Ibs of bone dust&amp;gt; and equal also to what a grazing cow annu- 



