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the eatsward of the reservoir. It strikes E. ro degrees N., and by 
making small excavations across the adjoining field it can be 
traced in this direction to the north and south road connecting 
Messina Springs and Orville. Here the serpentinous earth com- 
posing the dike can be readily found in the gutters on either side 
of the road and is easily distinguishable from the heavy red clay 
and greenish shale of the Salina rock through which it has forced 
its way. Continuing into the pasture to the eastward its strike 
can be followed with little trouble to a place about one-third of a 
mile east of the reservoir where the harder gypseous shales form 
a small bluff over the lower reddish shales. In the lower lands 
beyond I have as yet been unable to trace the dike. In the east 
side of the bluff it is quite distinct, its width as indicated by the 
yellow earth being 105 feet. In the absence of any distinct con- 
tacts it is probable that the width of the dike is less than this. 
Darton’s paper quotes the contractor as saying ‘ that the entire 
bottom of the reservoir, 200x250 feet, was covered with the 
greenish-yellow earth ’ also, ‘ that the blocks of rock varied great- 
ly in size, some being 20x50 feet.’ My experience with these dikes 
convinces me that it is unlikely that any one of the great wedge- 
shaped blocks into which the cooling peridotite contracted would 
be as much as 20x50 feet in size. On the other hand it is improb- 
able that an intelligent contractor would be greatly mistaken in | 
his figures in regard to this mass, especially as it was a hard, 
tough mass of rock making its excavation extremely difficult. 
Therefore it is altogether likely that this was a section of the dike 
itself extending across the excavation, and which to the workmen 
would seem like a great block imbedded in the softer serpentinous 
matter, or even in the argillaceous or calcareous Salina shales 
which make up a part of the excavated hill. According to this 
supposition the width of the dike did not greatly exceed 20 feet. 
The other blocks which were thrown out from the excavation in 
such quantities were undoubtedly the farther extension of the dike 
across the reservoir. These blocks furnished sufficient rock for 
building up the walls of the reservoir, a considerable surplus 
remaining. Because of the tendency of the peridodite to altera- 
tion it is surprising to see how well this rock is wearing in the 
