436 PROCEEDINGS OF BALTIMORE MEETING. 



this country and in England, and whose value is attested by the fact that 

 it has already passed through several editions. 



In the invention of mechanical appliances to facilitate petrogra})hic 

 work, Professor Williams showed especial aptitude. He devised an 

 electrical machine for cutting and grinding thin-sections of rocks, and 

 also aided in the perfecting of the only satisfactory petrographical micro- 

 scope manufactured in this country. 



When the World's Fair Commissioners of Maryland desired the prep- 

 aration of a volume in which the resources of the state should be suita- 

 bly presented, an appeal was made to the Johns Hopkins University, 

 and Professor Williams was appointed chairman of the committee which 

 had the matter in charge. He contributed largely to the book, writing 

 upon the geology and mineral resources of the state and preparing a 

 geological map which is a most important addition to our knowledge of 

 the geological formations. 



The work of Professor Williams upon the Piedmont area of Maryland 

 led to the discovery, in the South Mountain district of Pennsylvania 

 and its extension into Maryland, of ancient volcanic rocks of both acid 

 and basic types which present all the essential features of modern erup- 

 tives. This occurrence suggested the probable extension of similar rocks 

 along the eastern border of tbe continent, a point fully corroborated by 

 a proper interpretation of the older literature and a study of the ma- 

 terial specially collected by himself and others. It was the intention 

 of Professor Williams more fully to investigate this subject, and plans 

 had been formed for field observation in the north during the past 

 summer. 



During the last academic year extensive preparation had been made 

 for the publication of a general work upon the crystalline schists, which 

 would have presented the maturer views of Professor Williams upon 

 this important subject. An elaborate course of lectures was delivered to 

 his students, in which the outline of the prospective volume was given. 



Other lines of Avork were under consideration, but the end came before 

 they could be undertaken. 



Professor Williams was honored with membership in many scientific 

 societies. He was a corresponding member of the Geological Society of 

 London and of the French Mineralogical Society, and at its last meeting 

 was elected one of the vice-presidents of the Geological Society of America. 

 As one of the judges of award in the department of mines and mining at 

 the World's Fair, he was requested to prepare the report upon the ex- 

 hibits of minerals and gems. 



Professor Williams appeared often on public occasions, where his 



