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TO CONSTRUCT EQUAL FIGURES.

new figure, it gives us the point b. In the same way we may find theplace of every other point c, d, e, and draw the polygon abcde—aequal to ABCDE—A.

In this method there are three sources of error,—1st.the parallelism, and equal distance of the lines which formthe square; 2nd. in drawing the lines, with respect to theirbeing all perfectly straight at every point, and of an equalbreadth throughout; 3d. in measuring the position ofeach point.

These observations will make the artisan sensible howmuch the most simple methods are liable to error, andhow necessary it is in practice to acquire that skill, care,patience, and good judgment, that fineness of tact andperception, which no theories or methods can give. Cor-rectness is the characteristic of art in its greatest per-fection. It is not surprising, therefore, that ages of at-tention, and numerous trials, should have been requir-ed to construct, correctly, any machine, of which theprinciples are well known, and the form theoretically es-tablished, but the successful working of which dependson each part being made with great precision. Nationslittle advanced in those arts which depend on precision,find it very difficult to overtake people who have precededthem, even when they are at liberty to borrow their im-provements ; for every advance already made, serves themore skilful people as a means,—by making more correctinstruments, &c.—of hastening their progress, and dimi-nishing the chances of error in their operations. An ex-tensive and correct theory, judiciously applied to practice,can alone place those nations on an equality, which are notso at present; and can alone enable those who use it, toexcel the competitors who now surpass them in manufac-turing skill. To accelerate this application, is the greatobject of our present plan of instruction.*

* The reader should, perhaps, be reminded here, that theory willnot give precision in execution. There can be no doubt, judgingfrom the admirable elementary works which have been published,in France and Germany , both on the sciences and arts, that the