Cements of the Portland type differ in kind from those of the pozzuolanic class; they are not mechanical mixtures of lime and active silica ready to unite under suitable conditions, but consist of definite chemical compounds of lime and silica and lime and alumina, which, when mixed with water, combine therewith, forming crystalline substances of great mechanical strength, and capable of adhering firmly to clean inert material, such as stone and sand.
And they are coated with a substance that gives off an inert gas if they are exposed to fire, so they are effectively a fire abatement system.
I perceive that, when an acorn and a chestnut fall side by side, the one does not remain inert to make way for the other, but both obey their own laws, and spring and grow and flourish as best they can, till one, perchance, overshadows and destroys the other.
Hillebrand, who had noticed, in examining the mineral uraninite, that an inert gas was evolved when the mineral was decomposed with acid.
This means that the previous manufacture of sulphuric acid in the vitriol-chambers is done away with, but this apparently great simplification is balanced by the great cost of the Hargreaves plant, and by the fact that the whole of the hydrochloric acid is mixed with nine or ten times its volume of inert gases.
The play of brilliant colours and of ever-changing contrasts of light and shade on those rugged mountain-sides and on the surface of the sea itself might have been expected to appeal to the most prosaic. The surface of the sea is generally smooth (seldom, however, absolutely inert as the pilgrims represented it), but is frequently raised by the north winds into waves, which, owing to the weight and density of the water, are often of great force.
Sense experience is thus the constant action upon our minds of supreme active intellect, and is not the consequence of dead inert matter.
These appliances as indicated should not be unnecessarily expanded, but when expanded they should, wherever practicable, be converted into actively moving flying surfaces, in preference to fixed or inert dead surfaces.
As a bleeding, mortally wounded animal licks its wounds, they remained inert in Moscow for five weeks, and then suddenly, with no fresh reason, fled back: they made a dash for the Kaluga road, and (after a victory--for at Malo- Yaroslavets the field of conflict again remained theirs) without undertaking a single serious battle, they fled still more rapidly back to Smolensk, beyond Smolensk, beyond the Berezina, beyond Vilna, and farther still.
They have made this observation the basis of a practical method of separating helium from the other inert gases.