It is said that if a child's marble be placed in a kettle, it will attract the earthy particles, and prevent the encrusting of the sides of the vessel.
"He gathereth the waters of the sea together as an heap; he layeth up the depth in storehouses."—Psalm xxxiii.
763. Why is it difficult to wash in hard water?
Because the soap unites with the mineral matters in the water, and being neutralised thereby, cannot dissolve the dirt which we desire to cleanse away.
Because salt is a mineral which prevails largely in the earth, and which, being very soluble in water, is taken up by the ocean.
Lakes and rivers, also, even those that are considered fresh, hold in solution some degree of saline matters, which they contribute to the ocean.
As, in the evaporations from the sea, the salt remains in it, while the vapours fall as rain, and again wash the earth and carry some of its mineral properties to the ocean, the greater saltness of the sea, as compared with rivers, is accounted for.