Occasionally, however, is found the layer of blue rock resting immediately on the layer of phosphatic limestone, and where this is the case numerous faults and dips occur, showing a similar structure to the Mt. Pleasant formation typified. Again, in the central basin or brown rock region, the top erosion first disintegrated and then partially took off the upper layers of shale or flint, sometimes entirely, sometimes leaving it from one to forty feet thick, which accounts for the varying overburden. In some places the limestone layers were entirely soluble or reduced to clay and some acid condition of soil water dissolved the upper layers of phosphate and redeposited it in the boulder and stalagmite forms of the “white rock” found in Perry and Decatur counties and near Godwin, in Maury County, and the “boulder rock” found everywhere to greater or less extent but in especially heavy deposits near Nashville on the McGavock Place. These latter redeposit varieties vary in analysis from 50 per cent to as high as 90 per cent phosphate, and are uncertain as far as the general variety goes, though individual deposits varying in extent from one to twenty or thirty acres, are found of very uniform quality. The first phosphate rock discovered in Tennessee was the kidney formation that almost always attends the blue rock and black shale deposit. The eminent physician, naturalist, botanist and geologist, Dr. Gattinger, of Nashville, of revered and beloved memory, was first to recognize these as phosphate rock, but being much more interested in determining the family and pedigree of some new beetle or plant than in the commercial aspect of any mineral proposition, he never gave his discovery to the world, and only by his casual mention of the fact one day to Will Shirley and Maj. W. J. Whitthorne, of Columbia, are we able to give him credit for the knowledge. Dr. Safford, in his “Geology of Tennessee,” describes in detail both the blue and brown rocks geologically, referring to the blue rock as a blue fossiliferous limestone nearly always occurring under the Devonian shale; but no chemical investigations being provided for, he did not find out that it was a phosphate rock. Major Whitthorne and Mr. Shirley kept up a systematic hunt for a deposit of commercial value and finally the former located one on upper Swan Creek simultaneously with the discovery made lower down the same creek by Messrs. Bates and Childs. These latter gentlemen were insistent that the black shale, commonly called slate rock, so abundant in the highland rim country, was a form of, or indicative of the proximity of, coal, and at regularly recurring intervals they would send in particularly promising looking samples to Professor Wharton, of Nashville, for analysis. One day they dropped into their bag of samples a piece of blue rock which they informed Professor Wharton was nearly always present under the “slate,” and seemed to be a