which are alike essential to our national prosperity and individual comfort.

Stupendous as are the powers of the Steam Engine, they are so perfectly under control, and so nicely regulated, that it is made to separate the fine film of the silk-worm, and to realise the fairy fingers of fiction, by spinning an invisible thread! To use the elegant language of JEFFREY, "it has become a thing alike wonderful for its force and flexibility; for the prodigious power which it can exert, and for the ease and precision, and ductility with which it can be varied, distributed, or applied."

Notwithstanding the intense interest which must attach to this subject in every rational mind, but very few works on the Steam Engine have appeared before the public, and these do not possess such qualifications as to render them of much utility. Those of the cheaper class have taken too contracted a view of the subject, and are unaccompanied with investigations of the practical advantages or defects of the machines under notice; while those of the expensive kind are unnecessarily elaborate in their minute details, and their investigations are too abstruse for the comprehension of readers who have not made considerable progress in mathematical science. In the one case, therefore, the ardent seeker for information will meet with little more than amusement; and in the other, he will find the knowledge inaccessible, from the manner in which it is exhibited.

In the Treatise now presented to the reader, Mr. GALLOWAY has steered a middle course, and thereby avoided those defects which have rendered the labours of his con. temporaries of very limited utility. The work was originally published about two years ago, and it has since met with so extensive a sale, as to induce the Proprietor to

send forth a new and improved edition, after having undergone a careful revisal by its Author, who has taken the opportunity of introducing some interesting and important matter, which the readers of the first edition will readily perceive and appreciate. It contains all the matter of the first edition, but in a more correct form; consisting of descriptive accounts of all the various Steam Engines that have been invented since the time of Hero the elder, (who flourished 130 years before Christ,) down to the year 1827; together with a critical and minute investigation of their merits and defects. To this portion of the work, which forms the first section, Mr. GALLOWAY has added a second section on Steam Navigation, and a third on Locomotive Steam Carriages.

To the original work, thus improved, has been added, in the present edition, a copious APPENDIX, which has been supplied by Mr. LUKE HEBERT, whose avocation, as Editor of the Register of Arts, and Journal of Patent Inventions, peculiarly qualifies him for the task.

On the importance of the subjects introduced into the Appendix, it will be unnecessary to dilate, as the simple statement of their nature will at once carry conviction to the mind. They are divided into eight sections, viz.

The first section, treats of the nature and properties of steam and other vapours, whose elastic forces have been employed or proposed as mechanical agents for impelling machinery; this subject, of necessity, includes a dissertation on the interesting phenomena of heat.

The second section, contains some preliminary observations on the construction of apparatus for the generation of steam, with descriptions of all the important, among

the very numerous, boilers which have been recently invented, or become the subject of patent-rights; including also a dissertation on safety valves, with accounts of a variety of contrivances to prevent dangerous explosions.

The third section, relates to the constituent parts of steam engines generally, in which their offices are separately considered, and the relative proportions, construction, and arrangement, described.

The fourth section, contains interesting accounts of a variety of newly-invented machinery for the propulsion of steam vessels.

The fifth section, is descriptive of the various locomotive steam carriages that have been recently constructed, or that are at present under a course of experimental trials.

The sixth section, contains accounts of various engines in which the elastic force of the vapours of ether, alcohol, essential oils, as well as carbonic acid gas, atmospheric air, and water are employed to produce motive power.

The seventh section, is descriptive of a variety of steam engines, many of which having been invented since the date of the last engine described by Mr. GALLOWAY, may be regarded as a continuation of his History.

The eighth section, contains a detail of numerous experiments on the weight and strength of materials, besides a variety of tabular matter, conveying information of the greatest practical utility in the art of construction.

HISTORY

THE STEAM ENGINE.

FIRST SECTION.

THE Source from which the Steam Engine, in all its varied modifications, derives its power, is a property which water possesses of becoming expanded by heat. This property begins to operate at a temperature of 40° of Fahrenheit, below which it also possesses the opposite quality of expanding by the decrease of heat. When the temperature exceeds 40°, it remains fluid until heated to 212°; it theu acquires the power of passing off in an aeriform state, and becoming vapour or steam, which is an extremely light and elastic body, and may be retained in a close vessel of sufficient strength, even when it is capable, unconfined, of expanding itself to several hundreds of times the area of its prison. In its confined state, it exerts a force against the sides of the vessel proportionate to its compression; which force being applied to water, or any other matter intervening between the steam and the channel of escape, exerts itself on the intervening matter, and thereby puts it in motion.

This is the most palpable and evident property of steam, and there can be no doubt that mankind have been acquainted with it from the earliest dawn of civilisation. But there is another method of deriving power from steam,' which, though equally useful, is not so easily discerned as

the former. This is the faculty which it possesses of being instantly condensed by cold, and re-converted into water By this property a partial vacuum may be produced in a vessel which was, an instant before, filled with steam; and if we suppose a tube connected with that vessel, and a well not exceeding twenty-five feet below, the pressure of the atmosphere will act upon the surface of the water in the well, and thereby raise it up through the tube and fill the vessel.

When this latter property of steam was first known, it is now impossible to determine. In the earliest experiments, the expansive force alone appears to have been applied, and that merely in an ineffective toy, known by the name of the oelopile. The first individual on record who used it, appears to have been Hero, the elder, an Alexandrian, who flourished about one hundred and thirty years before the Christian era. In his work, entitled Spiritalia, or Pneumatica, among other ingenious discoveries, he describes a machine to which motion is to be given by the force of steam. It consisted of a hollow globe, having tubular arms, running in opposite directions. These tubes had an opening at different sides, near their extremity. The globe was suspended upon centres, fixed upon pillars. One of those pillars was hollow, as also was one of the centres or axes. Steam was introduced from a cauldron, or heated vase, which, issuing through the hollow column and axis into the globe, and so through the arms into the open air, produced a rotary motion, in the same manner as water produces that of Barker's mill.

In the dark ages which succeeded the overthrow of the empires of Greece and Rome, history furnishes no instance of an attempt to use the powerful agency of steam, until the year 1563, when one Mathesius suggested the possibility of constructing a machine by which it could be worked by steam. In the year 1597, a book, printed at Leipsic, describes a "Whirling Oelopile," which, it is suggested, is well adapted to dispense with the services of the turnspit dog.

Up to this date we cannot trace any thing important