NJDEP - NJGS - First Annual Report of the Geological Survey of the ...

76cellent effects. The dry-bank marls, it will be'observed, aredeficient in lime; phosphoric acid is found _in them in theusual amount. These specimens were from the first bed, andprobably the third layer. They have usually been thoughtequal to the wet.bank marls of the same bed, for a short time,but to wear out sooner. Other comparisons will suggest themselvesto the minds of inquiring farmers._l POISON n OR ¢1BURlCING _1 _IAR_S.Marls arc found in all parts of the stratum_which are saidtobe burning or po/_on in their properties; so ,much so as todestroy vegetation. In some eases where they have beenfreely applied to the soil: they have destroyed its fertility foryears. These marls are not confined to any particular layeror bed, but arc found in spots or patches in all of them. Thedark clays above and below the first marl bed also possessthe same properties_and being frequently mistaken forgenuinemarls, have done serious injury to crops upon which they havebeen applied. The same is true of the brownish clay, calledrotten stone, which is found on top of any of th0 la2(ers of the 'third bed. In all these cases the injurious effect is due to sulphateof iron (copperas),or to that substance mixed with sulphateof alumina (a kind of alum). The latter substance isnot near as common as the former. Eiflmr of them can beeasily distinguished by the taste; the copperas is well knownby its astringent, inky taste; the other by the taste of alum.When marls, or earths containing them, arc exposed to the air,yellowish white incrustations of these salts form oa their surfaces.If other tests are desircd_ take some of the marl andboil it in two or three times its weight of Water, in a cleanearthen or porcelain dish ; then strain thetwater Clearfrom themarl. The copperas and alum wi!l be in solution in the water.If some of this Water is poured into strong tea_ it will turn itblack ; if poured into lime water it turns it a dirty white ; andif added to the blue liquid made by pouring hot water onNEW JERSEY GEOLOGICAL SURVEY