Junction of Trap and Sandstone. 

 Fig. 1. 



105 



It appears from this sketch that there are seven dykes of trap cut- 

 ting through the sandstone in this town, and such seems to be the 

 case to a traveller passing through the town from Durham to Chesh- 

 ire ; but of these seven only two are principal ranges, the remaining 

 five being subordinate. The dyke at No. 1. fig. 1., is one of the 

 principal ranges, being of itself a continuation of Mont Carmel range 

 in Hamden. It enters Wallingford at the south west corner, pre- 

 senting precipitous ledges on the south eastern side, runs northerly 

 near the western boundary of the town, nearly, or quite its whole 

 length, and is probably connected with the high ridges between Mer- 

 iden and Southington, about four miles further north. The dykes 

 cutting through at Nos. 2, 3, and 4, are probably ramifications of the 

 one just described ; but although 2, and 3, are upon the surface, 

 about thirty rods distant from each other, I am inclined to the opin- 

 ion that they have a subterranean communication. 



The small dyke cutting through at No. 8, is seldom seen above 

 the surface, nor does it seem to be directly connected with any of the 

 other dykes. It makes its appearance at the summit and foot of a 

 blufi" about a mile south of the town, and also on the surface three or 

 four times north east fro'n the center, from a quarter to a half a mile. 

 At the northern point it seems to turn east, and pass under the strata 

 of sandstone, and a continuation of this same, or some other dyke 

 appears on the surface about three fourths of a mile onward in the 

 same direction, near Mr. Hill's Manufactory. Of this, and the dyke 

 last described at No. 4, I shall have occasion again to speak. 



The dyke at No. 9, enters Wallingford on the south side, from 

 Northford, and running nearly parallel to the eastern boundary, reach- 

 es more than two thirds the whole length of the town, and is possibly 

 connected with the range farther east. 



The range at No. 11, extends the whole length of the town, pre- 

 senting a high mural front on the Wallingford side through its whol* 



Vol. XXVII.— No. 1. 14 



