12 WISCOKSIN" ACADEMY SCIENCES, AETS, AKD LETTERS. 



two occurrences: (1) as a coarse admixture of felspar, kaolinite etc. 

 removed but a short distance from where it resulted by disintegra- 

 tion; and (3) as a fine-grained clay washed from its coarse material, 

 and not directly traceable to its origin. In New Jersey the great 

 thicknesses of plastic clays, forming the lowest member of the Cre- 

 taceous series, stretch in a wide band south westward across the 

 state from Staten Island Sound to the Delaware River. In places 

 these clays come into contact with the gneisses of the Archaean 

 belt crossing the state from northeast to southwest, and have evi- 

 dently derived their material from the wear of the previously dis- 

 integrated gneissic rocks. In these clay beds kaolin-like clays oc- 

 cur both in the assorted and unassorted conditions. The coarse or 

 unassorted kaolin "^ is dug at several places on both the main land 

 and island sides of Staten Island Sound. The bed is from two to 

 twelve feet thick, and is composed of coarse angular fragments of 

 quartz mingled with decomposed felspar and mica scales. It is 

 interstratified with other clay and sand layers, and lignite. The 

 finer New Jersey clays of the same series are largely used for mak- 

 ing fire-brick and the rougher kinds of pottery. Some of them ap- 

 pear to be sufficiently pure for the manufacture of porcelain.f Or- 

 dinary stoneware, porcelain knobs etc. are extensively manufac" 

 tured at Trenton.l The purity of these bedded clays as compared 

 with most others would appear to be directly due to their deriva- 

 tion from the disintegration of the gneissic rocks of theregiou, and 

 deposition near by where first formed. 



A recent discovery in Indiana has brought to light what appears 

 to be a valuable bedded clay, occurring under peculiar circum- 

 stances. The kaolin bed lies at the base of the coal measure con- 

 glomerate, in Lawrence county, Indiana, having a thickness of five 

 to six feet, one of which is pure white kaolin, the remainder being 

 more or less stained with iron and manganese oxides. Immediate- 

 ly beneath the clay is a bed of limonite iron ore. This clay appears 

 to replace a bed of limestone which has been dissolved away by 

 the action of carbonated waters. It has almost exactly the com- 

 position of kaolinite. With it are found lumps of the mineral 

 allophane, another hydrated silicate of alumina, with a larger per- 

 centage of water than kaolinite. 



* Geology of ISTew Jersey p. 249. _ f Geology of 'New Jersey loc. cit. 



t Geology of Xew Jersey p. 685. 



