264 
GEOLOGY OF THE SECOND DISTRICT. 
The lithological characters of trap are, 
1. Compact greenish masses with a slight granular texture. 
2. Greenish masses, fine grained, hut with needleform crystals. 
3. Trap, greenish grey, with nodules of the same material, which often separate readily from the mass: it is the first step 
towards a columnar structure. 
4. Greenish trap, divided into horizontal columns, hut rarely regular in the number of sides; they are triangular gene¬ 
rally, and very rarely pentangular, or similar to columns of basalt. 
The direction of the dykes is a point worthy of some attention, and there is quite a wide 
range in this respect. I notice a few, in order to acquaint the reader with their general 
range, omitting the localities. They are selected from all parts of the. county, and pursue 
the following courses: 
4, N. 60° E. 
2, N. 70 E. 
2, N. 50 E. 
2, N. 40 E. 
1, N. 75 E. 
2, N. 20 E. 
I have never observed a dyke which coincided in its direction with the strata, nor one whose 
direction was due north and south. The nearest to the latter direction is that of N. 20° E., 
which, however, it is rare to meet with; and the introduction of the single instance in the 
preceding column alters the average range, and reduces it to N. 50° E., while I am more dis¬ 
posed to receive the average direction as N. 64° E. 
One of the localities at which dykes are quite common, is Trembleau point, near Port 
Kent. This point is the termination of the great range of mountains from the southwest, and 
the hypersthene rock is exposed upon the shore of Lake Champlain. In the distance of half 
or three-fourths of a mile, sixteen dykes occur, the average direction of which is about N. 
60° E. Some of them are twenty feet wide, but frequently terminate in a number of subor¬ 
dinate branches. 
Another point where dykes are numerous, is Port Henry, where several may be observed 
in the small stream which comes in from the west, and flows over the ledge of limestone 
above the furnace. 
The largest and most important of the volcanic rocks belonging to the class under conside¬ 
ration, are found in the interior of Essex, near the sources of the Hudson river and Ausable. 
One of these I have described already, namely, the great trap dyke at Avalanche lake, which, 
in consequence of being the channel of a small stream, has been broken up to the depth of 
a hundred feet, and the process is still going on. 
In this region, in almost every direction, may be observed notches in the ridges, which are 
most of them produced by dykes, the materials of which have been removed, as at the lake 
just named. 
The general phenomena of dykes are those which accompany mineral veins; hence it is 
important to observe them : they are in fact, true veins filled with stony matter, and observe 
the same laws in regard to direction, shifts, faults, etc. as other veins. 
