8 



last two groups, show what is known in geology as jointed structure. 

 Joints are planes of fracture cutting directly across the stratification ; 

 the planes sometimes occur only a few inches from each other, and are as 

 often separated by as many feet. When the rock is removed from one 

 side of the joint, bold faces of rock are left on the other side cut as 

 smoothly as with a workman's chisel. Fine examples may be seen at 

 both approaches of the tunnel and at the cut north of Earlville, where, 

 for some distance, the track extends parallel with the planes of the 

 joints. 



5. Life was very abundant during the Hamilton period, and fossil 

 remains are common in all the groups. The leading forms are Brachi- 

 opods, Lamellibranchs, and Trilobites and a few Cephalopods and 

 Radiates. Plants are found quite frequently though of a low order. 

 The most common, are in the form of narrow, flattened stems often 

 branching, but with no trace of foliage, Portions of many of these 

 stems are now represented only by a line of ferruginous matter, as it is 

 a property of vegetable matter to collect and accumulate iron to itself. 

 Sufficient however retain their original structure to show that they 

 were once members of the vegetable kingdom. In the beds west of the 

 tunnel is found a great abundance of conical, fusiform, or oval masses 

 often presenting a scaly appearance, often with an axis of a lighter 

 color, or red from ferruginous deposits. Some are possibly mineral con- 

 cretions but most are probably some low form of plant life, perhaps 

 stems of Lycopodiaceee, or their allies. Animal remains especially 

 those of Mollusca may occur in three different forms: (1.) The shell 

 itself more or less transformed in structure or distorted in shape ; (2.) 

 The molds of the exterior ; and (3.) The shell being gone, the cast of the 

 matter composing the interior. The first two of course resemble each 

 other; the last is often so different in appearance as to be mistaken for 

 an entirely distinct species. The shell structure quite often retains its 

 original appearance, though the calcareous matter composing it is often 

 metamorphosed into calcite. The exterior crust of Trilobites is fre- 

 quently found, yet is probably very much darker colored than was the 

 original, possibly from the proximity to bituminous matter. The rock 

 retains finely the delicate markings of the Mollusca and the surface 

 pu notations in the crust of Trilobites and the facets of their compound 

 eyes are often wonderfully preserved. Fossils are often changed in 

 shape and appearance by pressure, and frequently two specimens of the 

 same shell, differently compressed, are mistaken for distinct speeies. 

 Orthoceras constrictum is the most common species of the Marcellus 

 shale and is sometimes found with the delicate Bryozoan, Aulopora 

 training around the shell. Homalonotus Bekayi, Balmanites calliteles 

 and various Brachiopoda characterize the Hamilton proper and Genesee. 

 The rock beds at the tunnel and near Earlville contain abundant fossil 

 remains and will well repay a careful search. 



6. Economical products of the Hamilton are few and of compar- 

 atively little importance. The Marcellus shale is frequently used in 

 place of gravel for walks and drives; the more substantial rocks of the 

 Hamilton proper are used for foundation walls of outbuildings, for 

 fencing and, formerly, to a limited extent for building ; the Tully Lime- 

 stone before alluded to is sometimes burned for lime. 



e. DRIFT. 



1. By drift is meant the usual superficial deposits everywhere cov- 

 ering the rocks and underlying the soil, not including the alluvium of 

 rivers and smaller streams. The character of the drift varies with the 

 geological locality as it is derived from the wearing away of rock for- 

 mations. Passing from Syracuse to Earlville one will notice a marked 

 difference in the character of boulders along the line of the road, espec- 

 ially those In situ in the cuts. While the pebbles and cobble-stones 

 may be somewhat similar at all points of the road consisting of rounded 

 fragments of sandstone, shale, limestone, and various crystalline rocks 



