50 ECONOMIC GEOLOGY. 
is Strafford, Vt., where copperas has been manufactured for the past fifty 
years. From that single locality on Copperas hill, thousands of tons of 
ore have been sent to market. The species is pyrrhotite, containing 39.5 
per cent. of sulphur, and is therefore less valuable than common pyrites, 
which has 53.3 per cent. of sulphur. 
There are several veins of pyrites in New Hampshire that can be 
successfully mined for the manufacturing establishments, especially as 
copper is usually associated with them. These veins are also nearer the 
market than those of Vermont, which are now mined so largely. Perhaps 
the most important of these is in the south-west part of Croydon. This 
has been visited twice,—in June, 1869, and May, 1870. The results of 
our examination are briefly these: The rock is micaceous and gneissic, 
one of the sub-divisions of the White Mountain series probably. It is 
elevated two or three hundred feet, on the south-east flank of Croydon 
mountain. Higher up is the quartzite, dipping at a high angle to N. 65° 
W. It probably overlies the sulphuret schist unconformably, as it cer- 
tainly does three miles farther north, the latter dipping 80° W. 10° S, 
@ne or two hundred feet east of the vein is a white gneissic rock, carry- 
ing an unusual amount of mica. This is parallel with it, and may be 
used as a guide in tracing it through the country. In this way the vein 
was followed for three fourths of a mile to the north, and from what was 
said to us, it is judged to extend equally far to the south. The vein has 
been opened to the depth of twenty-five feet. It was full of water at our 
first visit, but was drained at the second visit by means of a syphon. 
The vein mass is uniform in its width and composition. Next the hang- 
ing wall is six inches width of slaty layers, holding both copper and iron 
pyrites. Next succeeds two feet thickness of magnetic pyrites, or pyr- 
rhotite, very compact, solid, and nearly pure. There is no foreign min- 
eral present except small nodules of quartz. Next follows one foot ten 
inches of the same, less compact. Fourthly, is two feet thickness of 
gangue of quartz, or a micaceous mass carrying a large proportion of 
copper pyrites and zincblende. Below all this is a slaty mass three or 
four feet in thickness, similar to the upper layer, carrying considerable 
pyrites, which possibly may be utilized. The second, third, and fourth 
of these layers are valuable, and united amount to six feet in thickness. 
By Prof. Seely’s determination, the sulphur in No. 2 amounts to 37.68 
