PETROLIA 



Petrolia. Town of Ontario, 

 Canada. It is 50 m. from London, 

 being a station on the G.T.R. and 

 Michigan Central Kly.. and ob- 

 tained its name from the oilfields 

 in the vicinity. Industries include 

 the making of butter, bricks, etc., 

 and those connected with obtain- 

 ing and refining the oil. Pop. 3,500. 



Petrology (Gr. petra, rock , 

 logos, science) 'Science of rocks. 

 Also called petrography or litho- 

 logy, petrology is one of the divi- 

 sions of geology, overlaps the 

 kindred science of mineralogy, and 

 is concerned with the composition, 

 chemical and mineral ogical, the 

 structure, and the classification of 

 rocks. The full study of rocks in- 

 volves the use of the petrographic 

 microscope equipped for the study 

 of the optical properties of the 

 rocks ; a knowledge of chemistry 

 in all its branches ; of many 

 branches of physics, as crystallo- 

 graphy, etc. 



Rocks for examination under 

 the microscope are usually cut into 

 thin sections, and for chemical 

 analysis or tor separation purposes 

 crushed into small grains. In put- 

 ting a rock into its proper category 

 some characteristics which have 



versal sanction. In this work 

 every well-known rock is separ- 

 ately described. See Geology ; 

 Rocks ; consult also Petrology for 

 Students, A. Barker, 4th ed. 1908; 

 Text Book of Petrology, F. H. 

 Hatch, 6th ed. 1910; Manual of 

 Petrology, F. P. Mennell, 1913. 



Petronius (d. A.D. 65). Roman 

 writer, whose full name was Gaius 

 Petronius Arbiter. According to 

 Tacitus he received ,his last name 

 through being regarded as the 

 supreme judge or arbiter of ele- 

 gance in the vicious society in 

 which he lived. Although he 

 passed his days in sleep and his 



PETROPAVLOVSK 



nights in business or pleasure, as 

 governor of Bithynia he was a 

 capable administrator. Apparently 

 Petronius aroused the jealousy of 

 Tigellinus, and anticipated his 

 fate by opening his veins in a 

 warm bath. 



Petronius was the author of a 

 remarkable work of fiction, called 

 Satyricon, of which considerable 

 fragments have been preserved. 

 It describes the adventures of a 

 Greek freedman in various parts of 

 Italy, and shows a keen sense 

 of humour and an exceedingly 

 shrewd knowledge of human 

 nature ; it is valuable, moreover, 

 as throwing 

 an interesting 

 light on the social 

 life of the period. 

 Many of the 

 characters are 

 made to talk in 

 the plebeius sermo, 

 or language of the 

 common people, 

 and the difference 

 between this and 

 literary Latin 

 affords important 

 material for the 

 philologist. The 

 best known sec- 

 tion of the book 

 is the Cena Ttitnalchionis (Supper 

 of Trimalchio), which describes an 

 entertainment at the house of a vul- 

 gar parvenu. See Petronius Text 

 and Trans., M. Heseltine, 1913. 



Petrppavlpvsk. Name of two 

 towns in Asiatic Russia. (1) In 

 the govt. of Akmolinsk, on the 

 Ishim and the Siberian Rly. It has 

 soap works and tanneries, and a 

 trade in cattle, grain, wool, and 

 cloth. Pop. 20,000. (2) In Siberia, 

 on the peninsula of Kamchatka. 

 Pop. 400. 



to be considered by the petrologist 

 are its composition, hardness, 

 colour, crystalline or non-crystal- 

 line character, specific gravity, etc. 

 Rocks are divided into three 

 main classes, each in turn sub- 

 divided into many groups. These 

 classes are sedimentary rocks, 

 igneous rocks, and metamorphic 

 rocks. Examples of the first class 

 are sandstones, grits, clay, slate, 

 and marls ; of the second, granite, 

 olivine, and felspars ; and of the 

 third, schists and gneisses. Be- 

 cause the igneous rocks lack fossils, 

 their classification must ultimately 

 depend upon petrological investi- 

 gations. Such rocks comprise a 

 very large fraction of the earth's 

 crust, yet their origin is so obscure 

 and their characteristics are so 

 diverse that none of the suggested 

 classifications has received uni- 



Petioleum. 1. The petroleum bores at Campina, in the Rumanian oilfields. 



2. Summerland oilfield in California, where the wells are drilled 300 ft. below 



sea level and beyond the shore line. 3. Overflow of oil running into a natural 



reseivoir, Rumania 



