340 



New York at the "Woeld's Columbian ExposraoN, 



rapidly, and produce dust and mud. Shale is to be avoided, as it breaks 

 up rapidly, forming a sticky mud. Gravel, while rtiaking a serviceable 

 road, will not pack, and is not durable. If it has to be used some of 

 the difficulty may be overcome by cracking half of the pebbles. 



List of Specimens of Eoad Metals Exhibited. 



Trap or Diabase; Fort Lee, N. J. 



Granite ; Daniel E. Donovan, lona 

 Island, N. Y. 



Granite; Hudson R. Stone Supply Co., 

 Breakneck Mt. 



Granite; Port Chester, Westchester Co. 



Limestone, Tompkins Cove, N. Y. 



Limestone; P. Callanan, South Bethle- 

 hem, N. Y. 



Sandy Shale (Cauda-galli Grit) ; Knox, 

 Albany Co. 



Yellow Gravel; Staten Island. 



Geological Obelisk. 



A prominent feature of the mining exhibit was an obelisk of stone 

 from the various geological formations of ISTew York arranged in layers 

 of proportionate thickness on a scale of fifty feet to the inch, and of 

 which the proportions are those of Cleopatra's Needle in Central Park. 

 The idea of a geological column was first suggested by Prof. Hall, who 

 exhibited a pyramid at the ISTew Orleans Exposition in 1885 and 1886, 

 but it was found advisable by the superintendent to adopt a form and 

 plan different from that of Dr. Hall, and the proportions of the Egyp- 

 tian obelisk were adopted as exhibiting greater elegance of form and 

 being economical of ground space. The geological obelisk is composed 

 of cut stone from all the solid rock formations occurring in ISTew York 

 in their regular succession from the Archaean to the summit of the 

 Trias. The four sides of the obelisk show, by specimens from the vari- 

 ous localities the occurrence of the formations in the respective quar- 

 ters of the State, each formation being represented by a thickness pro- 

 portionate to its relative thickness in New York, the scale of the shaft 

 being fifty feet to one inch. 



The height of the shaft was twenty-six feet seven inches, and of the 

 pedestal three feet seven inches. 



The accompanying cut shows the form of the obelisk as well as the 

 different layers, their names and the relative thickness of the different 

 formations and groups. 



The courses are lettered as follows : 



Number of 

 Courses. 



Cap and Top Course, Triassic 

 Trap and Sandstone. 



V. Glean Conglomerate (Car- 

 honiferous). 



iCatskill 

 Portage 

 Chemung 

 Genesee 

 TuUy 

 Hamilton 



S. Marcellus 



R. Upper Helderberg, or Cor- 



niferous 



P. Schoharie 



O. Cauda galli 



N. Oriskany 



1 



121 

 5 

 5 

 1 

 1 

 4 

 1 



3 

 1 

 1 

 1 



Number of 

 Courses. 



M. Lower Helderberg 3 " 



L. Salina 4 



K. Niagara 2 



J. Clinton 1 



I. Medina 4 



H. Oneida 1 



G. Hudson River 5' 



P. Trenton 1 



E. Chazy 1 



D. Calciferous 1 



C. Potsdam 1 



B. Acadian 3 



A. Georgia 6 



Base, Archaean Granites and 

 Gneisses. 



as 



gs CD 



so a 





