299 



All these recent fresli water limes exist in gi-eat abundance in most 

 of the counties enumerated, as well as throughout the interior of 

 the State. In the northern part of Hillsdale, and the counties of 

 Washtenaw and Oakland, in particular, so extensive and universally 

 distributed are the beds of this useful mineral, that an attempt to as- 

 certain and enumerate all the places in which it exists, is unnecessary if 

 not impossible. 



But notwithstanding its wide distribution, the uses, and even the ex- 

 istence of this mineral, are so little known or heeded, even by those 

 who have most reason to appreciate its value, that I shall adventure 

 some remarks upon its application to practical purposes, and the method 

 of ascertaining its presence. 



For making quick lime, the value of marl and tufa is already appre- 

 ciated in those parts of our State which, like the counties under review, 

 are nearly destitute of limerock. Consequently these have supplied the 

 deficiency, and been applied to all the purposes of the best rock lime. 

 Though somewhat inferior in strength, the lime thus obtained is even 

 preferred for particular purposes. It is said, for instance, to be prefera- 

 ble as a wash, owing to its superior whiteness. Its real value is fre- 

 quently unden-ated from its not being sufficiently burned ; marl being 

 erroneously supposed to require a less degree of heat than limestone. 



Some of the largest deposits of tufa I have met with, are formed 

 along the banks of the Huron valley, between Ypsilanti and Dexter, at 

 several of which, large quantities of lime are manufactured. 



The circumstances which may give rise to the fonnation of either 

 tufa or shell-marl, where the same source of supply exists, is here 

 finely exemplified. Ledges of tufa occupy the elevated side of the 

 valley, while copious springs discharging from its foot, occasion a peat 

 morass between it and the river, beneath which is a body of soft marl 

 several feet in thickness. 



Impressions of leaves and bi-anches of trees, and even bones of ani- 

 mals, are numerous in some portions of the tufa, these substances hav- 

 ing evidently served as nuclei, around which the particles of lime were 

 deposited from the water of the springs ; thus, both giving an interest- 

 ing character to the bed, and illustrating its formation. 



The use of marl in agriculture is little appreciated, and may even 

 be said to be wholly unknown to the great body of the farmers of our 



