VEINLETS IN THE SILURIAN AND DEVONIAN 67 
met, thus forming a suture line near the center, but there is no 
evidence that such a suture was ever present in any of the veins 
under consideration. Large calcité crystals commonly extend 
without interruption from wall to wall, and in one vein a well- 
formed crystal of quartz, with a pyramid at each end of the prism, 
Fic. 3.—Calcite vein in limestone showing angular inclusion of the wall rock. 
Two-thirds natural size. 
was found extending across almost the entire width of the vein 
(see Fig. 5). 
The best evidence bearing on the origin of the veins is, perhaps, 
furnished by certain chert nodules containing veinlets of calcite, 
ranging up to 2 or 3 mm. in width, which do not extend into the 
inclosing limestone (see Fig. 6). The force separating the chert 
walls was applied so gradually that any stresses set up in the 
