34 
country divide the Limestones into hot and mild. The 
former, he savs, is no doubt magnesian, as it has similar 
effects on the soil, and is not so easily dissolved in nitric 
acid as the latter *. A little better acquaintance with these 
substances may make them known without analysis; and I 
have little doubt but that the farmers and their men, in the 
neighbourhood of the hot and mild Limestone, have some 
more or less intelligent way of distinguishing the one from 
the other, so as not to mistake—as lapidaries can tell white 
Agates from white Carnelians, although they confess they 
cannot tell how. The present specimens have a granular 
appearance, and, upon careful examination, are found to 
contain, or are indeed almost wholly formed of, little 
crystals agreeing more or less with the more perfect Pearl- 
spar—see ¢al. 19—and show the rhomboidal sides some- 
times tolerably distinct t+. The shell at the top of the plate, 
and the brownish piece in the middle, from Breden, as also 
the whiter piece below, have in these particulars the same 
structure. 
* One of the properties of Magnesian Limestone is its slow solution in 
Nitric Acid. 
+ Thus Mr. Tennant has discovered Pearl-spar to contain Magnesia ; 
which in part corrects Bergman’s analysis of that substance, whence so many 
mistakes have arisen. Heavy Limestone or Dolomite of Tirie he finds to 
contain Magnesia in a larger proportion than above. 
