The general employment of technical terms and phrases among scientists and mechanics, and the necessity for their use to avoid inconvenient paraphrases and involved sentences, make a thorough understanding and a discriminate use of these terms a duty to all who employ them. In our descriptions of machinery and processes we have always studiously avoided those terms, which, not being commonly used, were either generally unfamiliar or not self-defining. It may be that at times the article as published appeared to be too elementary in character, but it is better to use language understood by all than a patois intelligible to the initiated only. There are in use many technical terms, however, that of themselves are far more expressive than any phrase in common use, and these should be employed in preference to an explanatory sentence which reaches its point only by seeming to aim at another. In such cases the technicals are the proper terms. Many of them are not laid down in the dictionaries, and different ones are used in different sections of the country by men engaged in the same business; but some are so apparently demonstrative and in their sound so well convey the idea that they are always understood. For instance, if a smith i speaks of a " suant" heat, every one knows at once that it means a soft, even heat, permeating the mass of iron—the very sound of the word conveying the idea. The " bite" of an arid or file, the " hang" of a hammer, the " rake" of a turning tool, and many others beside those which, show their applicability by their derivation, are better than any phrase that is simply descriptive or definitive. But all technical terms to be useful should lie definite. Though a " stringer" may be a " beam," it docs not follow that a beam is a stringer. A, railroad " sleeper" may not be also a railroad " tie." A " bit" may be a plane iron or an instrument for boring wood. " Force" and " power" arc not synonymous, neither are " weight" and " pressure." So we might go on indefinitely, and give examples of the indiscriminate and improper use of technical terms. We have a letter before us in which the writer, speaking of his steam boiler, uses the terms " fire surface" and " heating surface " as synonymous. Another speaks of the " force" of steam and the " pressure" of steam, also as synonymous or interchangeable terms. It is sometimes difficult, under such circumstances, to really understand what is meant. In such cases it would be better to use language of a less concise but more explanatory character. Yet there is a pedantry affected by many in the use of technicals that is as annoying as it is pretentious. It is seen in the use of geometrical terms in defining well-known and familiar forms, and of algebraic formulas to state simple arithmetical problems. There are occasions when this is not only proper, but absolutely necessary for the defining of the subject. As to those who air their superfieialtics by a malapropos employment of all the technical terms they have been able to pick up, they do not deserve notice; such are beneath criticism and beyond improvement. But even our professional teachers, the compilers of manuals designed to aid the beginner, are open to the charge of pedantry, and not unf roquently to that of writing about what it is evident they do not themselves understand. It would lie unkind and harsh, perhaps, to refer by title to such works, but we have been several times much surprised to note the ingenuity of two, at least, of these authors in concealing their own ignorance while assuming to teach others. Nystrom, in his "Technological Education" says: " We frequently find most valuable formulas given by scientific men in such a shape that it requires to know more than the author in order to employ them; they are not only not trimmed to a practical shape, but even the meaning of letters is rarely explained in proper technical language." We are convinced that the reason why our mechanics do not generally take kindly to scientific education applicable to their department, is not because of a dislike to the subject, but because of the needless obstructions in the way of ambiguous and involved statements that seem to be made or presented in a form purposely designed to annoy, or carelessly calculated to mislead.