tau

For tubes of uniform section m is constant; for steady motion W is constant; and for isothermal expansion τ is constant.

Given any event e1, there is an event e2 and a time-interval τ such that, whenever e1 occurs, e2 follows after an interval τ.

Hence, since there are no infinitesimal time-intervals, there must be some finite lapse of time τ between cause and effect.

However short we make the interval τ, something may happen during this interval which prevents the expected result.

It further suggested the idea, that the sound of θ differed from that of τ, by the addition of h—which was wrong also.