With Air Vessel, A. D. 1675.

327

Chap. 8.]

thereof. The water is drawn in to the body of the pump at the hole F,at the time when the sucker is raised; and when the same is let down,the valve of the same hole shuts, and forces the water to pass through thehole into the tube G of which the valve being lifted up, the water entersinto the pot, and filling the bottom it enters through the hole into the tubeK N L in such a manner, that when the water is higher than the [orificeof the] tube K, and the hole of the tube G is shut by the valve, the air in-closed in the pot hath no issue, and it comes to pass, that when you con-tinue to make the water enter into the pot by the tube G, which is muchthicker [larger] than the aperture of the end L, at which it must issue, itmust needs be, that the surplus of the water that enters into the pot, andexceeds that which at the same times issues through the small end of thejet, compresses the air to find place in the pot; which makes that, whilstthe sucker is raised ■ again to make new water to enter into the body of thepump, the air which has been compressed in the pot drives the surplus ofthe water by the force of its spring, meantime that a new compression ofthe sucker, makes new water to enter and causes also a new compressionof the air. And thus the course of the water, which issues by the jet, isalways entertained in the same state.” The box or ehest had two pro-jecting pieces on each side, through which two staves were passed for theconvenience of carrying it. This small engine appears to have been inevery respect an effective one; the whole of the parts, both of the pumpand apparatus for working it, were well adapted to produce the best ef-fect. The goose-neck seems to have been formed of a species of balland socket joint.

No. 147. View and Section of a Fire -engine with Air Vessel. A. D. 1675.

One might suppose that when this account of the construction and ef-fects of air chambers was published to the world, and in the StandardJournals of France and England, that they would speedily have beenadopted'in fire-engines throughout Europe . Such, however, was not thefact; on the contrary, they appear to have remained comparatively un-known for nearly fif'ty years longer; for it was not tili the expiration ofthe first quarter of the 18th Century that they began to be much used, andsome years more elapsed before they were generally employed. We canonly account for this by the limited circulation of the scientific journalsnamed, and their being confined principally to learned men; who then asformerly feit indifferent towards mechanical researches : mechanics inthose days were no great readers, and the few who possessed a taste forbooks were commonly without the means to gratify it. It is, however,