70 
IOWA ACADEMY OF SCIENCES. 
the gneiss east of Mine Falls, where two areas exist: one a mile 
west of Nashua (Main street) and south of the canal, where out- 
crops occur at a large quarry, and in the hill just west of the 
cemetery. The other area omitted is in the northeastern part 
of the city itself, at Shattuck’s ledge, near the Merrimac river, 
a mile and a half from the outcrops just west of the city. 
It is possible that these two areas should be classed as one, 
since no outcrops exist between the two areas to tell what the 
rock between them may be. 
The line bounding Hitchcock’s ‘-Rockingham Mica Schist” 
seems to indicate the line between schist and gneiss, as if he did 
not recognize the slate as a separate rock from the schist. My 
northwestern line bounding the slate lies about parallel to his 
line bounding the Rockingham Mica Schist and a mile to the 
southeast of it. 
Strike . — On the map accompanying this paper numerous dips 
and strikes may be found recorded. It now becomes necessary 
to observe their relation to determine what folds may exist in 
the area, for there are no strata within the slate area itself 
whose repetition can indicate the structure. 
Within the slate area and in the gneiss along the northwest- 
ern boundary the strikes measured are much the same. North 
of Nashua there is slight evidence that the anticline there tends 
to form a nose; but ail other variations from N. 33° E. are such 
as a badly crushed area might represent; variations too small 
to be systematized even by minute observatiors at all points. 
This general similarity of strike indicates horizontal folds 
extending in the direction of the strike. 
A study of the dip along lines at right angles to the strike 
reveals the anticline of a fold running in the direction of the 
strike along the western half of the slate, while a syncline runs 
along the eastern half. These are here represented in a dia- 
gram. (Pig. 3.) 
