WILSON: MEDFOHI) DIKE AHEA. 
3(;i 
The present topography of the dike and of the adjacent country 
is very instructive. At the Medford end, proceeding north, there is 
a gradual rise from tlie Hood-plain of the Mystic river, just above 
tide level, to the summit of Pasture hill, one hundred and twenty- 
five feet higher, in a horizontal distance of about three hundred 
yards. As one crosses the summit, on his right he will find that the 
lull falls off almost abruptly towards Governor’s avenue, the grade 
being little less than that normally assumed by the talus slope of 
coarse-grained debris at the foot of a cliff; on the left the fall is very 
slight towards several ridges of felsitic rock, trending towards the 
northwest. For a portion of the length of the hill, at the northern 
end, a depression occurs on the diabase bePveen PasturO hill and 
thesej’idges. (Fig- 1, hl) 
Fig. 1. Sections transverse to the diabase dike. I. From about one hun¬ 
dred yards north of where Owen’s walk turns to join Forest street. II. From 
just north of the lower quarry on the west flank of Pine hill. III. From 
Pasturefliill, Medford. 
I and II, datum line one hundred feet above mean tide level; III, datum line . 
at mean tide level. 
a. granite, b. felsite, c. diabase, d. felsitic breccia. 
The descent on the northern slope of the hill, about ten degrees, 
is, relative to the ascent on the south, quite gentle, until the Hall 
road, fifty feet above mean tide level, is reached. Here the land 
again rises very abruptly thirty-five feet, the grade along Cedar Cliff 
road, twenty-eight degrees, being steeper tlian that on the eastern 
side of Pasture hill. Ascending this slope, we find on the left a 
