Proceedings. 1 83 



Prof. Winchell enumerated several theories that had been advanced 

 for the existence of the prairies, and stated that he believed the chief cause 

 is the extensive fires that rage annually or semi-annually over the prairie 

 region. There are facts that disprove every other assumed cause. It is ob- 

 jected by Mr. Upham, that tires do not, in the eastern and central states, 

 produce such treeless tracts, and that they prevail annually with great vio- 

 lence. Yet the eastern tires do not have such extensive level areas to spread 

 over, and to be carried by the w^ind with such speed. While tire is the prime 

 cause, this has to be supplemented by favoring topography and absence of 

 lakes, and perhaps by some diminution of rain-fall to produce the effects 

 seen in the western states and territories. Notwithstanding all other as- 

 sumed causes, fire is the only cause which, if repressed, allows the gradual 

 spread of forest trees over the prairies, as has been observed and attested in 

 many cases. 



October 8, 1889. 



The following were elected members: Prof. F. S. Jones, 

 A. L. Crocker, John Byers, G. H. Warren, R. J. Anderson, Dr. 

 E. A. Hutchins, Peter Christiansen, Horace V. Winchell, of 

 Minneapolis; Prof. Otto Lugger and Prof. D. N. Harper, St. An- 

 thony Park; Hiram W. Slack, Henry S. Baker, St. Paul; Prof. 

 L. H. Batchelder, Prof. H. L. Osborn, Hamline; Edward 0. Ulrich, 

 Newport, Ky.; Prof. S. Calvin, Cowa City; Chas. R. Keyes, Bal- 

 timore, Md. 



Secretary Hall gave notice that at the next meeting he should 

 move the following amendment to the by-laws. Article VII, Sec- 

 tion 1, viz: That the words "resident in the state" be stricken 

 rfOut, thus making the section read: "Any person may be elected 

 to membership," etc. 



A paper was read by N. H. Winchell, entitled "The so-called 

 Huronian rocks in the vicinity of Sudbury, Ontario," of which the 



following is the 



(abstract.) 



The paper gave an account of a joint excursion of the members of the 

 Oeological Society of America and of the American Association for the ad- 

 "vancement of Science from the Toronto meetings in August into the Huron- 

 ian region, northeast of lake Huron. As it was illustrated by specimens 

 which have the serial numbers of the State Geological Survey, and is there- 

 fore inseparable from them without damage, it has been published in the 

 eighteenth annual report of the survey (pp 47-58) with references to the cor- 

 responding rock samples. 



The paper rehearsed briefly the progress of opinion in respect to the age 

 of the crystalline rocks of the Northwest, calling particular attention to re- 

 cent re-examinations of the typical Huronian region, and to the opinions of 

 Irving and Lawson, and the establishment of names for rocks older than the 



