324 Oeo. H. Cook. —Smock. 
of the oflfice is unparalleled in the history of geological surveys 
in our country. The annual reports of the state geologist for 
the years 1869-1888 inclusive have given the records of the 
work done each succeeding year and represent the varied direc- 
tions in which the investigations of the survey have been 
guided by him. In 1878 the report on the clay deposits of the 
state- appeared. The need of detailed topographic surveys as 
a basis for geological maps and their value in tracing out the 
stratigraphical relations within a small territory were shown 
in the map of the clay districts of Middlesex county, the first 
one of that series of the topographic department of the survey. 
The severe tests to which that map has been put and its tried 
value to the fire-clay and potter's-clay industries of the state 
constitute one of the most potent arguments for the usefulness 
of geological surveys and exhibit both the sagacity and the 
prudence of Dr. Cook in his direction of the survey. 
The geological structure of the magnetic iron-ore beds in the 
northern part of the state, described in so clear and plain 
terms as to be of the greatest service to the iron miner and 
the iron-ore prospector, is another evidence of the practical 
direction of his investigations and of their service in develop- 
ing the mineral resources of the state. These deposits were 
described by Prof. Rogers as veins and unstratified. The 
surveys of Dr, Cook showed them to be bedded members, in 
the crystalline rock series ; and his later work indicated their 
occurrence in certain horizons in the Archsean group. To the 
geologist and to the mining engineer the full descriptions of 
the forms and location of these lenticular-shaped iron-ore beds 
are of the first importance, both in the study of the structure 
of the whole crystalline rock series and in the exploitation of 
the territory in search of additional ore supplies. The full 
and practical directions for the use of the magnetic compass 
in searching for ore and the magnetic survey of the state 
afford valuable data to the future explorer and suggest a more 
exhaustive survey in order to determine the horizon of the 
iron ores and their relation to the associated rocks. 
Dr. Cook was one of the first to discover the existence of a 
great terminal moraine in the eastern United States, and his 
first public announcement of it was in a paper read at the 
■^ Keport on the Clay Deposits of Woodbridge, South Amboy and 
otlier places in New Jersey." Trenton, 1878, 8vo, vui and 381 pp. 
