53 JOURNAIv OF THE 



bridg-e is assembled; so that no increase of stress is expe- 

 rienced, but the reverse and the width of chord can be 

 safely taken at G.G inches, or say 7 inches, for a depth of 

 16 inches, as lirst found. 



The maximum stresses in the ties and posts are of 

 course under a full loadingf of 14,000 pounds at each post. 

 The chord now bends downwards throughout so that it 

 cannot ^sustain near as much of the load (acting" as a 

 beam) as before. The strict investigation can be made 

 as above; but it may prove near enough in determining 

 the section of the ties (the posts evidently having an ex- 

 cess of strength) to suppose each post to carry the full 

 panel load in place of the strict value (14 — p), to the ties 

 and proportion them for the corresponding stress in an 

 end tie, as their section is uniform throughout. The sec- 

 tion given was determined in this way for an assumed unit 

 stress of 10,000 pounds i^er square inch. 



SOME LATE VIEWS OF THE SO-CALLED 

 TACONIC AND HURONIAN ROCKS IN 

 CENTRAL NORTH CAROLINA.^ 



BY H. E. C. NITZE. 



The region under discussion embraces a belt, from 8 to 

 40 miles in width, of metamorphic slates and schists, 

 extending from Virginia in a general southwesterly direc- 

 tion across the central part of North Carolina into South 

 Carolina. This area forms the principal gold ore belt 



^ For further discus^sion of this subject and for map showing the dis- 

 tribution of the rocks here described, scQ Bulletin 3 N. C. Geological 

 Survey, 1896. ' 



