Since it is now certain thata World's Fair will shortly be held within our city, and that we may confidently expect a competition with foreign rivals for the prize of superiority, we have resolved to give our readers a synopsis of the present condition of Machinery, Operatives' Tools, and other apparatus employed' n Manufactures, the Arts, and Handicraft in general. This account will not be limited to those in use in our own country, but will also comprise the newest improvements abroad, our aim being not to tell our artificers what they already know, but to give them information on subjects where they may be ignorant. Our ewn epoch is most opportunely suited for such a purpose, as the late World's Fair in London brought together not only the fabrics, but many of the tools and much of the machinery of the workers of different nations. From their inspection much has been learned, namely, by what means the artificer of one nation excelled the artificer of another, and where the superiority lay. Moreover, from the prizes offered, the inventive skill of different nations was stimulated, and consequently much improved machinery was exhibited from the various workshops of the world, that would otherwise probably have never been produced, at least not for a longer period of time. The universal competition acting as a stimulant to precocious invention. There have therefore been lately introduced several improvements in the machinery and tools of many branches of art and manufacture, with which, doubtless, a large portion of our arti-zans and mechanics are unacquainted. It will consequently be serviceable to those who intend to exhibit, at the approaching New York World's Fair, to know what has been already done, and what improvements have been made not only in America but also in Europe, as compatition may be expected from their people, as well as from our own. For this purpose we propose to give in our columns a series of articles on the above-named subjects, not merely a bare catalogue of names, but containing such information as will be of use to our readers. We must, however, premise that our remarks will, of course, be directed to those employments where striking improvements have been made ; as our aim is to furnish information, it would be useless to dilate where there is nothing to be said. Where no new improvements have been made, no fresh information can be afforded. As we observed before, our purpose is to make our people ac-quainted with many processes of which, per haps, they are ignorant, not from any deficiency on their part, but from natural circumstances over which they can exercise no control. Such collections as were exhibited in the London Crystal Palace, and will be, we expect, exhibited in the New York Crystal Palace, can not otherwise be amassed toge ther. Distance of country, difference of language, want of time, and want of pecuniary means, prevent that general international communication which would tend so much to the spread of knowledge, so that it is only by such extraordinary efforts as a World's Fair that the mechanical knowledge of each separate division of the world can be known. In addition to what has been already said, many improvements are unknown, from being confined to a single locality, and sometimes even to a particular factory; these we shall endeavor to bring out, if possible, from their obscurity for the universal good; others, although patented, are not generally known, from negligence in making them public, and this latter category includes a greater number of valuable improvements than might be supposed. Improvements being often dropped from want of encouragement, or want of means to publish their advantage. Moreover, if such information were more widely spread, much inventive skill that is now idly, or rather uselessly, employed upon inventions that have already been made, would be diverted to a more profitable direction. It is not uncommon for several individuals to be exercising their ingenuity in discovering what has been already discovered, and although their invention does them infinite credit on the score of talent, to find it anticipated on the score of personal benefit. We would, however, wish i1 to be understood that it is our intention tc t. give only a resume of the present state of ma chinery, c.,and that, therefore, particular inventions, unless of very material importance, cannot expect to be discussed. Unless some luch arrangement is determined upon, it would be an endless task to notice every new invention which claims to itself the fact of being an improvement. Those improvements, therefore, can only be noticed which have received the stamp of general approbation, or have gained the title by being brought into general use, or, finally, which bear evident proofs of deserving it. In the choice of these latter, discretion and judgment will be used, for it should be recollected that every change is not an improvement. However ingenious an invention may be, especially in machinery and working tools, it cannot be called an improvement unless it is a change for the better, to suppose otherwise would be a contradiction not only of sense but of words. We shall therefore conclude for the present, hoping, in the number of next week, to commence performing what we have promised in this.