By turns our purity inspires and our impurity casts us down.
This idea of impurity would seem a further proof of the African origin of iron.
In Judaism, as in other, especially Oriental, religions, the natural dislike of material defilement has been elevated into a religious sentiment, and made to support a complicated system of quasi-sanitary abstinences and ceremonial purifications; then, as the ethical element predominated in the Jewish religion, a moral symbolism was felt to reside in the ceremonial code, and thus aversion to impurity came to be a common form of the ethico-religious sentiment.
Gas leaves the retorts saturated with naphthalene, and its capacity for holding that impurity seems to be augmented by the presence of water vapour.
Sulphuretted hydrogen is a noxious impurity, and its complete removal from the gas is usually imposed by parliament.