56 
CASE 16. — Special grades of lubricating oils. These in- 
clude spindle, sewing machine, screw cutting and engine oils. 
They are light bodied and quick feeding as compared with the 
cylinder oils. 
CASE 17. — General heavy oils, including miners' oil, leather 
oil and various engine oils. 
CASES 18 AND 19. — Bye-products of petroleum. These in- 
clude paraffine wax, crude, semi-refined and refined, with illustra- 
tions of its uses for candles, matches, tapers, etc; axle grease, 
lantern oil, harness oil, ‘'miners’ sunshine,” for miner’s lamps; 
vaseline products, such as cerates, pomades, soaps and face 
paints. 
CASE 20. — ^Special grades of illuminating oils. These oils 
are designed to give the best light obtainable from kerosene. 
They are liquids of remarkable purity and brilliancy, the two 
finest being hardly distinguishable from distilled water in color. 
CASE 21. — High test illuminating oils. 
CASE 22. — Illustrations of some of the uses to which pe- 
troleum products are put. These include waxed paper for 
wrapping purposes, water proof coating for explosives, varnishes, 
wood stains and fillers, solvent for rubber cement, electric light 
carbons, and electrode. 
A series of Russian petroleums is also exhibited in this 
case. 
HALL 72. 
PLATINUM, GOLD, SILVER AND LEAD. 
The collections in this Hall comprise platinum, gold, silver 
and lead ores. Besides the typical ores many unique occurrences 
are represented here. In the examination of these, as well as 
ores of other metals, it should be remembered that the mineral 
or metal is frequently present in such minute quantities that it 
cannot be seen by the naked eye or even with the aid of an ordi- 
nary magnifying glass. Ores of the precious metals are com- 
monly, however, associated with certain mixtures of common and 
otherwise valueless minerals, known as gangue minerals, and by 
a careful observation of which associated minerals and of the 
neighboring rocks, the skillful observer may frequently recog- 
