66 
IOWA ACADEMY OF SCIENCES. 
were, however, sold at these figures. There are very large 
quantities of ore in sight in these mines, as even a brief inspec- 
tion clearly shows, and they are capable of yielding thousands 
of tons for some years to come. 
The output of the mines for the past year can be given only 
approximately. They have produced about 750,000 pounds of 
lead and from 3,000 to 3,500 tons of zinc. But it must be 
remembered that, as already stated, most of the zinc mines 
were closed during the past season. They are easily capable 
of yielding from 8,000 to 10,000 tons of ore annually. 
THE AREA OF SLATE NEAR NASHUA, N. H. 
BY J. L. TILTON. 
OUTLINE. 
Maps of Crosby and Hitchcock. 
The area briefly outlined. 
Description of the slate area. 
Description of the rocks. 
♦ .Section from Nashua northward. 
•Section along the Massachusetts line. 
Section west of Hollis Center. 
Section east from Runnells Bridge, and southeast from Nashua. 
Attempt to harmonize descriptions of Crosby and Hitchcock. 
Structure. 
Dip, strike, general section. 
Evidences of faults. 
Cause of metamorphism. 
Ma]js of Crosby and Hitchcock. — Crosby’s map of eastern 
Massachusetts represents an area of slate, or argillite, as it is » 
termed, ^running from Worcester through Lancaster and Pep- 
perell^to the New Hampshire state line. The eastern part of 
this argillite, two and one- fourth miles wide on the map, but 
four miles wide according to the text,* continues north into 
New Hampshire just west of the Nashua river. On the east 
of the argillite lies mica schist in an area very narrow (three- 
fourths' of a mile) near the state line, but much wider toward 
the southern part of the township of Dunstable. On the west 
*Orosby’SQ“ Geology of Eastern Massachusetts,” p. 137. 
