We have thus, from 1615 to 1653, shown, what sources were open to afford suggestions to the Marquis of Worcester’s wakeful and watchful mind, alive and on the alert to seize on every hint promising some enlarged and useful application. We come next to that part of his own statement, where he says: “so that having found a way to make my vessels, so that they are strengthened by the FORCE within them, and the one to fill after the other, &c.” “Vessels” may here apply to cisterns, receivers, boilers, &c., in short whatever appliances were used. But it is usually supposed to mean the boiler only, and hence the difficulty to understand how its safety should increase with the increased internal expansive _force_ of the steam. But allowance must be made for the general vagueness throughout the “Century,” and we must bear in mind that its language was not arranged to inform the public in respect to construction, but, as its author explicitly states, the several inventions are “set down in such a way as may _sufficiently_ instruct _me_ to put any of them in practice.” Now there is good ground for believing that the Marquis had a special meaning for the word “force,” as here applied, a word then used indifferently in its ordinary and in a technical sense, in the same sentence. This is particularly worth illustrating; firstly, because it shows a probability that the Marquis had, before 1655, designed some kind of safety-valve; and secondly, to remove the common supposition of the foregoing invention being utterly paradoxical. It has already been stated, that there is sufficient evidence to prove, that John Bate’s “Mysteries of Nature and Art,” had attracted the especial notice of the Marquis. He would be about 33 years of age on its first publication, and he wrote his Century about 20 years after its appearance, we may, therefore, readily see how likely it would be for him to adopt even its very style and language. John Bate says, at page 11:-- [Illustration: A forcer]