275 



the very atmosphere of the Mint imparts gold to everything -svithin 

 its walls, or that there was a want of the utmost care in the use of 

 vessels and reagents in these operations. 



Perhaps the most curious result of all is that which remains to be 

 stated. 



Underneath the paved city of Philadelphia there lies a deposit 

 of clay, whose area, by a probable estimate, would measure over 

 three miles square, enabling us to figure out the convenient sum of 

 ten square miles. The average depth is believed to be not less than 

 fifteen feet. The inquiry was started whether gold was diffused in 

 this earthy bed. From a central locality, which might afford a fair 

 assay for the whole, the cellar of the new market-house in Market 

 Street near Eleventh Street, we dug out some of the clay at a depth 

 of fourteen feet, where it could not have been an artificial deposit. 

 The weight of 130 grammes was dried and duly treated, and yielded 

 one-eighth of a milligramme of gold; a very decided quantity on a 

 fine assay balance. 



It was afterwards ascertained that the clay in its natural moisture 

 loses about fifteen per cent, by drying. So that, as it lies in the 

 ground, the clay contains one part gold in 1,224,000. 



This experiment was repeated upon clay taken from a brickyard 

 in the suburbs of the city, with nearly the same result. 



In order to calculate with some accuracy the value of this body of 

 wealth, we cut out blocks of the clay, and found that on an average, 

 a cubic foot, as it lies in the ground, weighs 120 pounds, as near as 

 may be; making the specific gravity 1-92. The assay gives seven- 

 tenths of a grain, say three cents' worth of gold to the cubic foot. 

 Assuming the data already given, we get 4180 millions of cubic feet 

 of clay under our streets and houses, in which securely lies 126 

 millions of dollars. And if, as is pretty certain, the corporate limits 

 of the city would afford eight times this bulk of clay, we have more 

 gold than has yet been brought, according to the statistics, from 

 California and Australia. 



It is also apparent that every time a cartload of clay is hauled out 

 of a cellar, enough gold goes with it to pay for the carting. And if 

 the bricks which front our houses could have brought to their sur- 

 face, in the form of gold leaf, the amount of gold which they con- 

 tain, we shopld have the glittering show of two square inches on 

 every brick. 



We have inquired but little into the researches of other experi- 

 menters in this line. Some years ago it was stated that Mr. J.cn- 



