IN offering these pages to the public, it may be expected that in conformity with the usual custom, I should state briefly the general nature and purpose of my subject, noticing the principal works which have already been written upon it, and lastly, the method and arrangement adopted in the execution of my task.

It may, therefore, be premised that the practise of the Art of Turning constitutes the basis of the work, whilst the various mechanical arts associated with it, or derived directly from it, will form collateral branches of comment and inquiry.

The importance of the lathe towards the promotion of the useful arts will be readily admitted, when it is considered how large a proportion of the indispensable objects we daily use, are either immediately produced by its agency, or in a greater or leas degree are dependent upon this machine. Indeed it may be truly asserted, that nearly all solid objects, (particularly those of wood or metal,) in which the circle or any of its modi-fications can be discovered, arc the offspring of the lathe, which produces, from solid materials of every description, an almost endless number and variety of forms, the origin of which can be traced to that most simple, symmetrical, and best defined of all the mathematical figures, the circle.

No perfect or definite form is so easily or so accurately described as that of the circle; thus the compasses by placing one point on a sheet of paper or other material, and sweeping the pencil or style around the same, trace a line which returns into itself, and form a figure equi-distant at every part from the point within, termed its center; or the proceeding may be reversed, by giving the paper a rotary motion beneath the pencil, which is kept stationary, whereby the same figure is produced.

The latter modification constitutes the principle of the lathe; the fixed center of the compasses being equivalent to the fixed axis upon which the solid material is made to revolve by some mechanical arrangement; the tracing pencil is supplanted by the cutting tool, which being held in a certain position towards the axis of rotation, cuts a circular groove in the revolving material; or if it be applied to its edge, reduces the object to a circular form.

This proceeding includes the three primary elements which constitute the ordinary practice of turning; namely, an immoveable axis; the revolution of the material upon that axis; and a fixed position of the cutting tool, in order that it may pare away all the parts of the body that oppose it. But the application of these elements must be modified and extended, if we desire to produce a compound form, such for instance as a vase; the first two elements, or the fixed axis and the revolution of the material, are retained, whilst the tool is moved by slow degrees along the outline or contour of the vase, both within and without, so as to remove all those parts of the material which are in excess, or project beyond the ideal line to be produced: and the continued, though temporary application of the tool, at every individual point of the vase or other object, renders every section taken at right angles to its axis, a circle. There are other less important modifications of the lathe, in which the position of the axis is changed and rendered moveable during the revolution of the work, as in oval and rose-engine turning, but these variations need only be adverted to here.

The art of turning will be admitted to be an auxiliary of great importance in the economy of mankind, as to it we are more or less immediately indebted, for nearly all the component parts of the machines and instruments, which are conducive in a thousand ways to the support and clothing of the person, and the advancement of the mind.

For instance the engines which are now habitually and almost universally employed, in converting the numerous raw products of the earth to our most urgent, as well as to our most refined necessities and pleasures could scarcely exist, in the absence of the tools indispensably required for the accurate production of the circular parts, that enter so largely and in so important a manner, into their respective structures.

Again, without the lathe we could hardly possess another machine in which the circle abounds, namely the steam-engine, which like an obedient automaton endowed with power and endurance almost unlimited, is equally subscr\icnt, either in converting the raw materials into their manufactured products, or in transporting them, in cither state, across the ocean, or over the surface of the earth, along with the individuals, through whose energies they have been collected, transformed, and distributed.

Nor amongst our obligations to the mechanical arts, is that the least which is afforded by them in the cause of science, the delicate apparatus for pursuing which, is due to the skill of the mechanist, whose instruments enable us to discover, and likewise to measure the planetary orbs, or to inspect in the cabinet the wonderful particles of the world we inhabit; and by means of which we find our earth to be teeming with creation, exquisite symmetry, and beautifully adapted to the purposes of organic life; indeed, in whatever direction, and with what-ever purpose the man of science may look, prospects of similar grandeur, and of equal wonder, still open in endless succession to repay the labour of research, an effort wherein the instruments, (due in great measure to the turner's skill,) are only secondary in importance to man's own mental faculties. How largely also the circle and its many combinations enter into the elegancies and ornaments of life: more particularly in the useful and indispensable creations of taste and fancy obtained from the wheel of the manufacturer of pottery and porcelain and more or less so in all the arts of construction and embellishment, whether applied to the useful and agreeable purpose of ornamenting the costume of mankind; assisting towards prosecution of the art of engraving; or in that most important of engines the printing-machine, which disseminates, in millions of channels, the thoughts and speculations of the human mind; throughout all of which, the turner's primary element, the circle, is equally pervading and indispensable.