GEOLOGICAL, AND NATURAL HISTORY SURVEYS. 823 



first elaborate account of the mineral resources and geology of the 

 State. The geological map was based upon the county athxses and 

 was perhaps as accurate as could be expected under the circum- 

 stances. 



Even at the time of publication of this report it was recognized by 

 Doctor Cook that, through lack of lime and means, many important 

 problems had been neglected altogether or only briefly touched upon. 

 A series of annual reports was, therefore, ph\nned, which should 

 successfully deal with important topics. These reports have been 

 published each year since 1869, each volume, as a rule, treating of 

 several topics rather than a single one. 



Since 1868 the work has been divided into three groups — economic, 

 topographic, and scientific. No hard and fast lines have, however, 

 been drawn between the groups, and many of tlie ])roblems investi- 

 gated belong equally well in either one or even in all three. 



The topographic work, in the preparation of accurate maps, has 

 been of great economic value, and much which, on its face, was of a 

 purely scientific nature, has led to results of great practical value 

 on the economic side. For convenience, hoAvever, there was grouped 

 under economic work only those investigations which bore most 

 directly upon the wealth of the State. The topographic work in- 

 cluded the surveys and publication of geological maps, while under 

 scientific work was placed those investigations which had chiefly an 

 educational aspect, either in increasing human knowledge or in 

 giving wider currency to facts of geologic and geographic interer-t. 



Economic icork. — The nature and extent of the iron ores of the 

 State received much attention from Doctor Cook. Magnetic surveys 

 were made in numerous instances and at frequent intervals; all the 

 active mines were visited, samples of the ore collected, and numer- 

 ous analyses made. The reports for 1873, 1874, 1879, 1883, 1890, and 

 1896 contain the most important papers on this su]:>ject. Since 1896 

 brief annual reports only have been made to cover the operations of 

 the active mines. 



Clay deposits received early attention. Considerable data was 

 published in the report of 1868, and 10 years later Doctor Cook wrote 

 a special report on the Woodbridge and Amboy clays, which was the 

 first elaborate report on this subject by any survey and was for years 

 regarded as standard. The greensand marls of the southern portion 

 of tlie State, being in the early days of the survey in great demand 

 for fertilizers, the first geological map was made to include the loca- 

 tion of all the marl belts, and in the reports of 1868, 1873, and 1886 

 the deposits are described and numerous analyses given, as well as 

 instructions for their use. In the report for 1892 there was an inter- 

 esting paper concerning the origin of the beds. Betvreen 187ri and 



