534 REPORT OF NATIONAL MUSEUM, 1890. 



exhibited, one (59867) from Washington, Pennsylvania, and the second 

 (59853) from Aurelius, Ohio.* 



The name paraffiue is given to a wax-like hydrocarbon obtained by 

 a process of distillation from petroleum, and occurring sparingly na- 

 tive. 



Ozokerite is also a wax-like hydrocarbon compound occurring spar- 

 ingly in seams in rocks and sometimes associated with beds of coal or 

 other bituminous products. It is used mainly as a substitute for bees- 

 wax and as an insulator. But two localities are here represented. 

 Utah (No. 67205) and Galicia, Austria (No. 12908). Asphaltum or bi- 

 tumen is an amorphous mixture of hydrocarbons, derived presumably 

 from decomposing organic matter, but belonging to rocks of no particu- 

 lar geological horizon. It has been found in gneissic rocks in Sweden. 

 Specimen No. 27832 is from the Niagara limestones underlying Chicago, 

 Illinois. No. 10678 is from the so-called Pitch Lake on the island of 

 Trinidad, No. 66590 from Cuba, and No. 59345 from Scotland. 



Albertite and grahamite are names given to closely related, coal- 

 like, hydrocarbons occurring in pockets and veins, and which are sup- 

 posed to have originated by the distillation of carbonaceous matter in 

 the underlying shales. (Specimens Nos. 36138 and 59924 from Nova 

 Scotia and West Virginia.) 



Amber and gum copal are vegetable resins altered by fossilization. 

 They are used for jewelry (see gem collection southwest range) and in 

 the manufacture of varnishes. 



B. — ROCKS FORMED AS SEDIMENTARY DEPOSITS AND FRAG-MENTAL 



IN STRUCTURE. 



The rocks of this group differ from those just described in that they 

 are composed mainly of fragmental materials derived from the break- 

 ing down of older rocks, or are but the more or less consolidated ac- 

 cumulations of organic and inorganic debris from plant and animal life. 

 The group shows transitional forms into the last as will be illustrated 

 by certain of the limestones and the quartzites. They are water de- 

 posits, and as a rule are eminently stratified or bedded, although this 

 structure is not always apparent in the hand specimen owing to its 

 small size. 



This great group of nonmetamorphic sedimentary rocks is one of the 

 most important in geological science, since it is by means of the still 

 unchanged organic forms (fossils) they contain that the paleontologist 

 has been enabled to study the past history of the globe, to discover the 

 multitudinous changes which have taken place in the climate, charac- 



* Under the title of " The Trenton Limestones as a source of petroleum and nat- 

 ural gas in Ohio and Indiana " (Ann. Rep. U. S. Geol. Survey, 1886-87, part ii, pp. 

 483-662), Prof. Edward Orton gives a most instructive summary of our knowledge on 

 these subjects, and to this paper those desiring further information are referred. 



