This machine of Huyghens is of great interest, not simply because it was the first gas-engine and the prototype of the very successful modern explosive gas-engine of Otto and Langen, but principally as having been the first engine which consisted of a cylinder and piston. The sketch shows its form. It consisted of a cylinder, _A_, a piston, _B_, two relief-pipes, _C C_, fitted with check-valves and a system of pulleys, _F_, by which the weight is raised. The explosion of the powder at _H_ expels the air from the cylinder. When the products of combustion have cooled, the pressure of the atmosphere is no longer counterbalanced by that of air beneath, and the piston is forced down, raising the weight. The plan was never put in practice, although the invention was capable of being made a working and possibly useful machine. [Illustration: FIG. 10.--Huyghens's Engine, 1680.] At about this period the English attained some superiority over their neighbors on the Continent in the practical application of science and the development of the useful arts, and it has never since been lost. A sudden and great development of applied science and of the useful arts took place during the reign of Charles II., which is probably largely attributable to the interest taken by that monarch in many branches of construction and of science. He is said to have been very fond of mathematics, mechanics, chemistry, and natural history, and to have had a laboratory erected, and to have employed learned men to carry on experiments and lines of research for his satisfaction. He was especially fond of the study and investigation of the arts and sciences most closely related to naval architecture and navigation, and devoted much attention to the determination of the best forms of vessels, and to the discovery of the best kinds of ship-timber. His brother, the Duke of York, was equally fond of this study, and was his companion in some of his work. Great as is the influence of the monarch, to-day, in forming the tastes and habits and in determining the direction of the studies and labors of the people, his influence was vastly more potent in those earlier days; and it may well be believed that the rapid strides taken by Great Britain from that time were, in great degree, a consequence of the well-known habits of Charles II., and that the nation, which had an exceptional natural aptitude for mechanical pursuits, should have been prompted by the example of its king to enter upon such a course as resulted in the early attainment of an advanced position in all branches of applied science.