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136

HESSIAN ENGINE.

not considered to be essential. The elector formed an engine without it, which was placed in the court of the Hessian academy of arts and sciences, that' raised water into a reservoir at the height of seventy feet, whence it descended in a jet into a fountain placed in the court of the building.

Papin dedicates a division of his descriptive treatise to a comparison of the value of the elector's engine with that of his rival's; Savery's merit is acknowledged with candour, his mechanism is allowed to be effective and meritorious, and his idea to be original. With so much ingenuousness, therefore, it would be invidious to enter into a discussion, to show that the points in which the Hessian engine differed most from Savery's, were those which were the least worthy of imitation.

CHAPTER FIFTH.

“THERE IS NO ARTIST, OR MAN OF INDUSTRY, WHO MIXETH JUDGMENT WITH HIS PRACTICE, BUT FINDETH, IN THE TRAVAIL OF HIS LABOUR, BETTER AND NEARER COURSES TO MAKE PERFECT THE BEAUTY OF HIS WORK, THAN WERE AT FIRST PRESENTED TO THE EYE OF HIS KNOWLEDGE.”-Markham.

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ADMIRABLE as Savery's engine was, when compared to any thing that had been employed to raise water before its invention, many serious objections lay against its usefulness. These, however, arose more from an inherent defect in the principle of its action, than from a want of ingenuity in selecting the most proper methods for carrying the scheme into practice.

There could be no question, but that, even in the form described in Savery's book, its power was to be used at a much cheaper rate than that of animals. It was capable also of being increased and concentrated far beyond the point to which animal power could possibly be concentrated ; huta short experience was only necessary to show that steam, of the elasticity used by Savery, was a dangerous agent; that on account of its expansive power, the apparatus was often deranged; a circumstance which, at the time, operated greatly against it, not only on account of the difficulty

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defectS OF SAVERY'S ENGINE.

but of the expense that was incurred in providing workmen to make the repairs; for it was not then, as now, that persons were to be had experienced in the erection and reparation of steam apparatus in every part of the kingdom.

Its first use, and location, if we may be allowed the term, was unfortunate for the inventor on another account. The fuel which was to call this power into being had to be brought from a distance. This enhanced its price, and made the comparison with animal power still more unfavourable in an economical view.

Several causes now began to be assigned for the waste of fuel. The steam, which was admitted into the cylinders, was condensed by coming into contact with the surface of the water which was to be elevated. It was observed that this water, to a small depth, required to be heated to the temperature of the incumbent vapour, before “ the steam was strong enough” to expel it from the receiver. The great condensation, arising from the vapour coming into contact with the cold sides of the receiver, entered also into the general estimate of the causes of the expense of fuel. These were considered grand sources of the " great waste of steam," and it followed, of as many of coals as were burned to form it.

The attempt to obviate some of these evils was not unaccompanied with serious disadvantages. When the sides of the receivers were cooled but moderately by the effusion of cold water on the outside of the vessels, the vacuum within the cylinder was proportionably imperfect; for, unless its sides, as well as the surface of the water, were cooled sufficiently, vapour of considerable elasticity still remained, and counteracted the pressure of the atmospheric column. This, in fact,

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