112 The American Geologist. ^"&"«^' ^^oi 
and various l^y-products. lliey are accompanied by engrav- 
ings (plates from published handbooks) showing mines, mills 
and furnaces from which the various samples were taken, 
tach collection begins with a series of the ore-bearing miner- 
als. This is followed by a series of the ores in which the ore 
mineral is evident to the eye, and this, in turn, by selected sam- 
ples of the ores as mined, and in which, as is often the case, 
the ore-bearing mineral is wholly inconspicuous. 
The economic collection is somewhat exceptional on account 
of the prominence given to what are classed as the non-metallic 
minerals (i. e., minerals not used as ores of metals). There 
are thus exhibited, grouped by visage and kinds, very complete 
series of natural pigments, abrasives, salts used in fertilizer 
and chemical manufacture, sulphur and sulphur ores, clays, 
limes and cements, diatomaceous earth and tripoli, asbestos, 
both crude and manufactured, mica, fluxes used in metallur- 
gical operations, coals and other hydro-carbon compounds, etc. 
Some prominence is given to the rarer earths and minerals 
which are now coming into more general use, as monazite, 
cerite, zircon, spodumene and other lithia minerals, celestite, 
uranium compounds etc. These collections are described in 
detail in the handbook above mentioned, from which plate i of 
this article is taken. A feature which has thus far been largely 
overlooked in collections of this nature, is a consideration of 
water as a mineral and its exhibit among other economic min- 
eral products. One case is given up to a display of this na- 
ture, selected to show kinds and geographic distribution in the 
United States. 
Another collection which will bear special reference is that 
of crude petroleum. This comprises upwards of 300 samples, 
some of which are of historical interest, as a sample, in the 
original package, of the "medicinal oil" from Little Rennox 
creek, Kentucky, put up in 1856. The collection is arranged 
to show (i) variations in specific gravityand (2) color, (3) 
geological horizons, and (4) geograpliical distribution. A 
small series of distillation products is also shown, though here, 
as in other instances, the strictly technological side is from ne- 
cessity, largely omitted. This collection is accompanied by 
maps showing the known distribution of petroleum and bitu- 
minous products throughout the world, and a small collection 
of oil sands and bitumen-l:)earino- rocks. 
