38 MICHIGAN ACADEMY OF SCIENCE. 



liECENT ^^■(J1{K OF THE GEOLOGICAL SURVEY. 



IJY ALFRED C. LANK. 



i^incc tlic last iiiocliiiji- of the Academy we have issued volume 7 of 

 oui- rej)or(8 whicli contains reports on Monroe, Huron and Sanilac coun- 

 ties. Taking these three counties together, one can form a very fair con- 

 ception of the course of events in the retirement of the ice from the 

 southeast i)art of ^Lchigan. Consideiable j)rogress has been made in 

 delineating the topography of the bed rock surface, and it is 

 worth noticing that there does not seem to be a very close harmony 

 l)etween the bed rock topography and tlie direction of the ice motion. 

 In the Huron county report I liave called attention to the wasting 

 away of the eastern shore of Huron county and am led to an estimate 

 of the age of the Great Lakes which is considerably less than 1(1,000 

 vears. 



This is a jioint wliere the various local members of the Academy 

 may be of gi-eat assistance in calling oni- attention to geological action 

 now going on which may enable us to compute the length of the post- 

 glacial time. IM'of. Davis' work on the jtcculiar botanical distribution 

 in Huron ((tunt}- has already been called to your attention and l*rof. 

 Sherzer's work on the glass sand of ^lonroe county has already proved 

 of great ])ractical value. I expect to see the glass industry grow in 

 Michigan. But I will not dwell long ui)on volume 7, for it can speak 

 for itself, except to call your attention 1o the fact that in the Sanilac 

 county report by Dr. Goi'don is an account of the famous stone wall 

 near Cass City which has been widely lieralded in the daily press as a 

 relic of the prehistoric race, but is iji reality nothing more than an 

 ice push wall. 



Passing to matter which has not yet been put in i)ress ollicially, I 

 Avould call your special attention to the brilliant work of I'rof. Davis 

 on our marl deposits tetuling to show that among many of the various 

 possibh' or true factors in marl formation the efticient one is the 

 work of Alga'^ in ])roducing the beds of great value. He will bring 

 it befoi'e you hei-e in anotlnu' section. Mr. Taylor has jtublished a study 

 of the glacial and surface geology of Lapeer county in the Lapeer 

 <'ounty Clarion, and through the work of Mv. Taylor and Mi-. Leverett 

 foi' the United States Geological Survey we shall soon have a mass of 

 detailed facts for surface geology. 



In .hine, lOOO, I jiublished a sliort article in the American Journal of 

 Science giving results of the tests of increase of temperature at Uay 

 City. It i)roved to be 1 in (IT' for :'.,r)00'. Jfecently an o])poi'tunity of- 

 fered to get the same giadient at Ulieboygau and we fctund that froni 

 a mean annual femi>eiat iiic of 41.0 at the surface, the tem])erature 

 rose to (!!.() ^ F. at about 1,.'>(>0' below. It gives nearly the same gradient, 



1 Journal of (Geology, 8 : No. 6, Sept.-Oct., 1900. 



