Empiricism, hitherto the only guide, if indeed a guide at all, was replaced by exact scientific knowledge; the connexion of each phenomenon with a controllable cause was established, and rule-of-thumb and quackery banished for ever by the free gift to the world of the results of his researches.
Besides the attainments mentioned above, in respect of operative progress, many important revisions of older rule-of-thumb knowledge have come about, and not a few other substantial discoveries.
Tilt of sights in field guns owing to the sinking of one wheel had long been recognized as a source of error, and allowed for by a rule-of-thumb correction, depending on the fact that the track of the wheels of British field artillery gun-carriages is 60", so that, for every inch one wheel is lower than the other, the whole system is turned through one degree - a_ hXl ?
As with cafetiere coffee, the golden rule of thumb here is a rounded dessertspoon, or seven grams, per cup.
A rule of thumb is that the whole system is likely to cost about £ 1000 per installed kilowatt.