870 REPORT OF NATIONAL MUSEUM, 1897. 



1 



The cryptocrystalliiie variety of quartz comprises a considerable 

 list of minerals: Opal, agate, chalcedonj^, flint, chert, hornstone, begin- 

 ning with the finest and purest and graduating down according to the 

 relative impurities and differences in mode of combination. Changes 

 in color run through the entire spectrum, and are due princii)ally to 

 the presence of metallic oxides. Iron is chargeable with most of them, 

 but green is credited by Dana to nickel, and purple to manganese. If 

 there were no impurities or foreign matter in it, the flint would be 

 nearly clear- white. 



MICROSCOPIC EXAMINATION OF FLINT. 



The author has shown that the rock called flint is found alike in 

 America and Europe; that it occurs in the two countries in both 

 nodules and strata, and in both is found in limestone as well as in 

 chalk. He proposes to continue the examination by comparing the 

 structure of the rock in the two countries, and to that end has caused 

 to be made thin sections of the flint fiom several of the mines and 

 quarries mentioned, and these subjected to microscopic inspection and 

 description by Dr. G. P. Merrill, head curator of the department of 

 geology in the U. S. National Museum. These sections have been 

 enlarged by the aid of the microscoi)e, and are shown in the pho- 

 tographic plates (16 to 22) duly identified, with the name, number, and 

 locality. Accompanying them are Dr. Merrill's descriptions, Avhile 

 Plates 23 and 24 show the original specimens from which the thin sections 

 were taken, appropriately marked for identification and comparison. 



We have now shown that the chemical constituents, the kind of 

 deposit, nodules and strata, in limestone and chalk, general appearance, 

 mode of mining and of use were practically the same during prehistoric 

 times in America and in Europe. If the microscopic examinations 

 show the rock from both countries to be of the same cryptocrys 

 talline structure, the ijrincipal, if not the sole difference being in the 

 degree of purity (or, rather, impurity), the author ventures to suggest 

 that there is nothing gained by making a distinction of names between 

 the flint of Europe and that of the United States, and that the distinc- 

 tion, if made, is so finely drawn p'^ to be impracticable for use by the 

 archieologists who deal with the material. 



These microscopic sections have been i^resented so that their struc- 

 ture can be compared and their similarity demonstrated: 



Plate 16, fig. 1, represents a specimen of flint from Brandon,^ fig. 2 

 is from Grimes Graves, and fig. 3 from Dorchester, all from England. 



Plate 17, tig. 1, is from Havelse, Denmark; fig. 2 is from Mouy, 

 Meudon, France, while fig. 3 is from Spiennes, Belgium. 



Plate 18, fig. 1, is from Grand Pressigny, France; figs. 2 and 3 are 

 from Flint Ridge, Licking County, Ohio. 



' Specimen fig. 1, on Plate 16 (flint from Brandon), is modern. All others are pre- 

 historic, at least ancient, specimens. 



