530 THE POPULAR SCIENCE MONTHLY. 



marvelous stories of its penetrating powers. They have been known 

 to assert that, if an empty and hermetically sealed glass bottle be placed 

 within the sheds where such stones are being cut, it will shortly be 

 found with a fine white deposit of the dust upon the bottom and on 

 the inside, and no argument can convince them that it came there 

 otherwise than through the pores of the seemingly impervious glass ! 



The quarrying of slate for roofing purposes is an industry of 

 comparatively recent origin in the United States, few of the quarries 

 having been operated for a longer period than twenty or thirty 

 years. The earliest opened and systematically worked are believed 

 to have been those at West Bangor, Pennsylvania, which date back 

 to 1835. The abundance of slate tombstones in many of our old 

 churchyards, however, would seem to prove that for other purposes 

 than roofing these stones have been quarried from a much earlier pe- 

 riod. It is stated, moreover, that as early as 1721 a cargo of twenty 

 tons of split slate was brought into Boston from Hangman's Island in 

 Braintree Bay, which may have been used wholly or in part for roof- 

 ing purposes ; but the greater part of the material for this purpose 

 was imported directly from Wales. It is interesting to note, in this 

 connection, that, daring the business depression of 1876-'80, almost 

 the entire product of the American quarries was exported to England, 

 where it sold for even less than the Welsh slates, though necessarily 

 at very small profits. The return of more prosperous times, however, 

 created a local demand, and the export trade hak been largely de- 

 creased accordingly, though considerable quantities are still sent out 

 to the West Indies, South America, England, Germany, and even New 

 Zealand and Australia. 



At present not far from $3,328,150 are invested in the slate-quar- 

 ries of the United States, and the value of the annual product is some 

 $1,529,985. 



Pennsylvania is the leading State in this industry, her quarries be- 

 ing located in Lehigh, Northampton, and York Counties, in the eastern 

 part of the State. These slates are all blue-black in color ; as are also 

 those from Maine, Massachusetts, and Maryland. The Vermont slates 

 are of a greenish or purple color, while those of New York are mostly 

 purple and red, the latter color being found in extensive deposits near 

 Granville, in Washington County. 



Besides for roofing purposes, slates are used for billiard-tables, 

 mantels, floor-tiles, flagging, and in the manufacture of school-slates. 

 For the last-named purpose a soft, even-grained stone is required, and 

 almost the entire supply is at present brought from Pennsylvania and 

 Vermont. 



Of late years, the business of marbleizing slates for mantels and 

 fireplaces has become an important industry. All kinds of stones can 

 be imitated by this process, but that most commonly seen is the green 

 verd-antique marble and the variegated marbles of Tennessee. Like 



