John Francis Williams.— Kemp. 151 
ences in rock types throughout one great, single, eruptive mass, 
which is shown in its central part to be a trachyte containing 
hypersthene and labradorite, but which passes toward the borders, 
at times into liparite, at times into andesite. 
Professor Klein desired Williams to go to Berlin, become his 
assistant, and continue his career in Germany. For a time in 
1886 the offer was accepted, but finally Dr. Williams returned to 
his home, and in 1887 became director of the technical museum 
of the Pratt institute in Brooklyn. The duties consisted in arrang- 
ing and caring for very excellent collections of minerals and rocks, 
but the desire for wider opportunities for scientific investigation 
led him in 1889 to become honorary fellow at Clark University, 
Worcester. While in this relation he received overtures from 
professor J. C. Branner, director of the geological survey of Ark- 
ansas to describe the igneous rocks of the state. Dr. Williams 
secure leave of absence from Clark and entered on his Arkansas 
work as a volunteer, without salary, in October, 1889. In the 
summer of 1890 he was made honorary docent at Clark. This 
title, like his previous one, carried no salary with it, and merely 
afforded him a work room and headquarters, which, however, were 
soon transferred to Little Rock. Evidently his relations with the 
University were not regarded as anything very serious, for no 
mention of them appears in his final report. 
Dr. Williams found a wealth of interesting material in Ark- 
ansas, and as the result of his collecting he published in 1890 
the papers on Manganopectolite and Eudialyte cited below. In 
the fall of 1890 he returned to Arkansas and completed his work, 
remaining, with one or two trips east, until the summer of 1891. 
He had meantime accumulated the materials for his final and 
greatest work, Volume II. of the Annual Report of the Geologi- 
cal survey for 1890, and entitled the Igneous Rocks of Arkansas. 
The volume, which was distributed in December, contains 432 
pages, 391 of which are by Dr. Williams alone. They give an 
accurate and exhaustive petrographic description of the syenites, 
elaeolite-syenites, leucite-syenites, the variations of all three, and 
describes the basie dikes which pierce them. Perhaps the great- 
est interest lies in the identification of leucite in these rocks, and 
in establishing Cretaceous leucite-syenites as a new variety, espec- 
ially as leucite has hitherto been considered to be limited to the 
later voleanic rocks. The report is accompanied by beautifully 
