32 REPORT OF THE 



Yery . many private citizens, besides the surveyors before 

 referred to, have already communicated most valuable informa" 

 tion on various points, which will be incorporated into my final 

 report. Mr. James S. Lawson, of Disco, Oakland county, has 

 furnished a description of an ancient lake terrace which is 

 found traversing that part of the State; and I would be glad to 

 commend this example to others who have the opportunity to 

 make observations upon such phenomena. 



Mr. A. 0- Currier, of Grand Rapids, has aided me materially 

 in arriving at a knowledge of the succession of strata pene- 

 trated in the salt borings of that place He has further pro- 

 vided me with a printed catalogue of the mollusca of the 

 Grand River Valley, accompanied by a nearly complete suite of 

 specimens 



Mr. Martin Metcalf, of the same place, has likewise, in his 

 correspondence, furnished me with important notes on the salt 

 borings, and critical remarks on the parallelism of strata. 



I am indebted to Dr. DeCamp, of the same place, for a fine 

 collection of geodes from the Grand Rapids limestone, and for 

 fossils; and to Prof. E. Danforth for the loan of his collection of 

 fossils from this and other States. 



Dr. G. A. Lathrop, of East Saginaw, has contributed impor- 

 tant aid in the carefully preserved series of borings taken from 

 the first salt well at that place; in specimens and suggestions 

 bearing upon the geology of the vicinity of Saginaw Bay; in 

 facts and statistics illustrating the salt manufacture in the 

 State, and by the loan of a suite «f fossils 



To Dr. H. C. Potter, superintendent of the salt works at East 

 Saginaw, I am similarly indebted for important facts connected 

 with the salt manufacture at that place. 



Mr. Henry D. Post, of Holland, Ottawa county, has furnished 

 me with observations on the outcrops of the Marshall sandstone 

 in his vicinity. 



Hon I. P. Ghristiancy, of Monroe, has sent the survey some 

 interesting fossil remains from the Monroe limestone; and also 

 statistics relative to the products of his quarries in the town- 



