These tongues are magnetized by the inducing action of a strong horse-shoe permanent magnet, S N, which is made in a curved shape for the sake of compactness.
Its simplicity and compactness recommended it immediately for communication between ship and shore and for intermarine communication generally.
Indeed, mathematicians now reserve "continuity" as the term for the latter kind of continuity; the mere property of having an infinite number of terms between any two terms is called "compactness."
The compactness of the series of rational numbers is consistent with quasi-gaps in it - that is, with the possible absence of limits to classes in it.
Now, owing to the necessary inexactness of measurement, it is impossible to discriminate directly whether any kind of continuous physical quantity possesses the compactness of the series of rationals or the continuity of the series of real numbers.