The breathless silence of the multitude was now broken by thunders of hurras, that drowned the hiss of the escaping steam and the rolling of the engine-wheels. To reduce the surprise and delight excited on this occasion to the universal standard, and as an illustration of the extent to which the value of property is sometimes enhanced by the success of a mechanical invention, it may be stated, that, when the Novelty had run her two miles and returned, the shares of the Liverpool and Manchester Railway had risen _ten per cent_. But how easily may the just expectations of an inventor be disappointed! Although the principle of _artificial draught_--the principle which gave to the Novelty such decided superiority in speed--is yet retained in all locomotive engines, the mode of producing this draught in our present engines is far different from that introduced by Ericsson, and was discovered by the merest accident; and so soon was this discovery made, after the successful display of the Novelty engine, that Ericsson had no time to derive the least advantage from its introduction. To him, however, belongs the credit of having disproved the correctness of the once established theory, that it was absolutely necessary that a certain _extensive_ amount of _surface_ should be exposed to the fire, to generate a given quantity of steam. The remarkable lightness and compactness of the new boiler invented by Ericsson led to the employment of steam in many instances in which it had been previously inapplicable. Among these may be mentioned the steam fire-engine constructed by him in conjunction with Mr. Braithwaite, about the same time with the Novelty, and which excited so much interest in London at the time the Argyle Rooms were on fire. A similar engine of greater power was subsequently constructed by Ericsson and Braithwaite for the King of Prussia, which was mainly instrumental in saving several valuable buildings at a great fire in Berlin. For this invention Ericsson received, in 1842, the large gold medal offered by the Mechanics' Institute of New York for the best plan of a steam fire-engine. In the year 1833 Ericsson brought before the scientific world in London his invention of the Caloric-Engine, which had been a favorite subject of speculation and reflection with him for many years. From the earliest period of his mechanical labors, he had been in the habit of regarding heat as an agent, _which, whilst it exerts mechanical force, undergoes no change._ The steam in the cylinder of a steam-engine, after having lifted the weight of the piston, contains just as much heat as it did before leaving the boiler,--minus only the loss by radiation. Yet in the low-pressure engine we turn the steam, after having performed its office, into a condensing-apparatus, where the heat is in a manner annihilated; and in the high-pressure engine we throw it away into the atmosphere.