An attempt is now made to illustrate and explain the details of engine-making. The author knows by experience that there is no work in any language which enumerates a sufficient number of details concerning engine-construction. We have written instructions about everything connected with the subject, except concerning the actual manipulation of the tools and appliances employed for the purpose.

The subject, as considered in the Mechanician, is rather extensive, and, in order to give satisfaction both to mechanics and learners, it is necessary to treat each individual piece of machinery distinctly, to consider it as something that must be forged, previously to being shaped and put into its place. The forging of the article is often of much more importance and expense than any after-operation ; and although all acknowledge that some practical instructions on the subject are needed, it is also acknowledged that none exist. The only one among us who has written anything reliable on forging is Holtzapffel. And even this industrious writer makes no mention of engine-work in its details. He commences his chapter on smith's work with a five-ton paddle-shaft; a subject which is rather sublime and overpowering, if not very comprehensible to a learner. The more rational and easy method of teaching forging, so that the instruction may be useful, is by first explaining the construction of those portions of a steam-engine which have simple forms only. When these are made tolerably familiar, is the time to introduce the compound ones.

This mode of dealing with the subject is adopted throughout the whole of the Mechanician to the end: consequently the plan of the work is quite original.

Probably it is impossible for any single writer to exhaust such a tedious and intricate matter; for this reason, the author considered it prudent, in order to admit a large amount of information on the subjects treated, to make the number of those subjects limited. And to make such a literary work new, in the proper sense of the term, we should endeavour to write about those branches of engine-making on which the least is written. These are forging, lining, planing, slotting, turning, and screw-cutting; a sufficient number for any one individual to manage properly.

The work comprehends three principal parts. The first part is devoted to forging, and a detailed description of engineers' tools and appliances. And, in addition to descriptions, sketches and detailed instructions are given in the several methods of making the tools that are mentioned.

The second part includes the application of the tools to the practice of engine-making.

The third part consists of details of mechanical processes which are not usually included in engine-making.

This arrangement is convenient to learners; because the names of tools and appliances must necessarily be frequently made use of in the second and third parts, and those who do not happen to know the particular form and method of making a certain tool, will refer to the first part for the desired information.

The details of the work commence with forging such simple articles as bolts and nuts, keys, straps, screw-keys, and similar articles. Several methods of making each article are mentioned, so that individual makers of small work may select the plan most suited to their requirements. The next treated are joint-pins, slide-valve rods, weigh-shafts, excentric-rods, piston-rods, connecting-rods, links, cross-heads, reversing-gear, paddle-shafts, crank-shafts, screw-shafts, propeller-shafts, and other shafts, small and large; the small being first introduced in order to make the work progressive and instructive to learners and to those who may not have previously studied engineering.

After the forging the various modes of shaping and fitting are introduced. These include drilling, slotting, planing, turning, and screw-cutting; also drill-making, cutter-making, boring-tools, screwing-tools, lathe-tools, planing-tools, slotters, shapers, excavators, and other assistants in the necessary process of adapting pieces of machinery to each other, such as dies, screw-plates, die-nuts, and taps.

Skilful mechanics must kindly bear with details which may be particularly valuable to those who require them, and may be highly interesting to students and others who are commencing the business. And it will be acknowledged that details are absolutely necessary to make he work more or less useful to mechanics generally.