Associated with natural gas is petroleum, and Pittsburgh 
has always been one of the most important centers for the 
development of oil fields. Our booklets have given in detail 
the rise and progress of the oil and gas development, the 
particulars of which have greatly surprised people who 
thought themselves thoroughly familiar with the great oil 
and gas industry. 
Without coal it would have been impossible for the iron 
and steel and oil and gas industries to start and grow, for 
this form of fuel is of vital importance, and it is no wonder 
that the First National Bank’s booklet on Coal had a wide 
reading. 
Many other Pittsburgh industries have been discussed, 
cne of the businesses perhaps less known but of great im- 
portance, being Radium, which formed the subject of a 
booklet. Then came Food Products; the extent of Pitts- 
burgh’s interest in the production, preservation and distri- 
sition of food making a booklet of decided importance 
In the present issue a number of “Diversified Products” 
of Pittsburgh and its environs are discussed, with particu- 
lars of the origin of the businesses, the location and cost of 
the plants, the officers of the concerns, and the number of 
men emploved in the several businesses 
ALUMINUM COMPANY OF AMERICA 
There is a wonderful romance about aluminum, the 
silver-white metal of extreme lightness, familiar to all, 
through its use in the manufacture of domestic articles, as 
well as in articles which are not often seen about the house. 
Not every one, however, knows that aluminum is the most 
common element in nature, with the exception of oxygen 
and silicon. About 89, of the earth’s crust is aluminum, 
and it is twice as plentiful in nature as iron, for it occurs in 
many minerals, clays and earths, but no process has yet 
been discovered of extracting the metal from common clay, 
although chemists have heen working on the problem for 
vears.