In the middle of the seventeenth century fire-engines indeed were still very imperfect. They had neither an air-chamber nor buckets, and required a great many men to work them. They consisted merely of a sucking-pump and forcing-pump united, which projected the water only in spurts, and with continual interruption. Such machines, on each movement of the lever, experience a stoppage, during which no water is thrown out; and because the pipe is fixed, it cannot convey water to remote places, though it may reach a fire at no great distance, where there are doors and windows to afford it a passage. At the same time the workmen are exposed to danger from the falling of the houses on fire, and must remove from them to a greater distance. Hautsch, however, had adapted to his engine a flexible pipe, which could be turned to any side as might be necessary, but certainly not an air-chamber, otherwise Schott would have mentioned it. In the time of Belidor there were no other engines in France, and the same kind alone were used in England in 1760. Professor Busch at least concludes so[605], from the account then given by Ferguson, who called Newsham’s engine, which threw the water out in a continued stream, a new invention. In Germany the oldest engines are of this kind. Who first conceived the idea of applying to the fire-engine an air-chamber, in which the included air, by compressing the water, forces it out in a continued stream, is not known. According to a conjecture of Perrault, Vitruvius seems to speak of a similar construction; but Perrault himself acknowledges that the obscure passage in question[606] might be explained in another manner. The air-chamber in its action has a similarity to Hero’s fountain, in which the air compressed by the water obliges the latter to ascend[607]. I can find no older fire-engine constructed with an air-chamber than that of which Perrault has given a figure and description. He says it was kept in the king’s library at Paris, and during fires could project water to a great height; that it had only one cylinder, and yet threw out the water in one continued jet. He mentions neither its age nor the inventor; and I can only add that his book was printed in 1684. The principle of this machine, however, seems to have been mentioned before by Mariotte, who on this account is by some considered as the inventor; but he does not appear to have had any idea of a fire-engine, at least he does not mention it.