SCIENTIFIC SURVEY. • 273 



part of Ellsworth, for three miles along Union river, the strata 

 dip northerly from 30° to 50°, and upon the east side in Hancock, 

 the strata dip 15°-20° northerly. At the shore of Union river 

 south of the Post Office in the village these mica schists dip 

 45° N. W. 



We now come to a change in the dip. In the north part of the 

 village on a hill the strata dip 70° S. 15° E., so that we have here 

 a synclinal axis, whose line runs along the course of Main street 

 in Ellsworth village. It is because the strata have been pushed up 

 almost upon their edges on the north side of this axis, that the hill 

 in the north part of the village exists, although further north it has 

 been largely worn away by the waters of Union river. Essen- 

 tially this dip prevails in the rock as far as its northwestern limit, 

 near C. Jarvis' house, a trifle more than three miles from Main 

 street, or just about half the distance from the Trenton Toll Gate. 

 It is worthy of notice that there are just as many feet thickness 

 of the strata on one side of this axis as on the other, since where 

 the dip is half as great the distance is double. A reference to the 

 section in Fig. 43, will show this fact most clearly. 



We have calculated the thickness of the strata upon both sides 

 of this axis, and will give the process. We shall be careful to 

 have the result too small rather than too large. Taking the west 

 side first — we have before us the problem, given the dip of the 

 strata for a known distance to find the thickness. It is done by 

 the solution of a simple case in Trigonometry. Given the hypothe- 

 nuse and one of the angles of a right angled triangle to find the 

 base, which is the thickness of the strata. Now the dip is 70°, 

 Deduct from this ten degrees for the possible original inclination 

 of the layers from the first deposition, and five degrees more for 

 possible errors, (for we find ourselves always inclined to state the 

 dip too high,) and we have 55° as the true angle for calculation, 

 and three and a quarter miles for the hypothenuse. The result is 

 13,000 feet, in round numbers, for the thickness of the north side of 

 this axis. Now the average of the dips upon the south side, tak- 

 ing into account the very small dip at Oak point, which must be 

 supplied for a small part of the distance, and then deducting the 

 fifteen degrees as before, must be 25° as the true angle for cal- 

 culation. Taking six and a half miles for the hypothenuse, we find 

 the base to be 13,600 feet in length in round numbers, or a little 

 more than two and a half miles of vertical thickness of strata. The 



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