Lectures on the Steamengine Author:Dionysius Lardner Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: LECTURE III. Defects of Savery's Engine ? Newcomen and Cawley?The Atmospheric Engine? Condensation by jet discovered ? Operation of the Engine ? Humphrey Pott... more »er's Invention to make the Engine work itself. (29.) In order duly to appreciate the value of improvements, it is necessary first to perceive the defects which these improvements are designed to remove. Savery's steam-engine, described in the last lecture, considering how little was known of the value and properties of steam, and how low the general standard of mechanical knowledge was in his day, is certainly highly creditable to his genius. Nevertheless it had very considerable defects, and was finally found to be inefficient for the most important purposes to which he proposed applying it. At the time of this invention, the mines in England had greatly increased in depth, and the process of draining them had become both expensive and difficult; so much so, that it was found in many instances that their produce did not cover the cost of working them. The drainage of these mines was the great object Savery proposed to effect by his steam- engine. It has been already stated, that the pressure of theatmosphere amounts to about 151bs. (4) on every square inch. Now, a column of water, whose base is one square inch, and whose height is 34 feet, weighs about 151bs. If we suppose that a perfect vacuum were produced in the steam-vessels v v' (fig. 8.) by condensation, the atmospheric pressure on i- would fail to force up the water, if the height of the top of these vessels exceeded 34 feet. It is plain, therefore, from this reasoning, that the engine cannot be more than 34 feet above the water which it is intended to elevate. But in fact it cannot be even so much ; for the vacuum produced in the steam-vessels v v' is nev...« less