Page:On Mr. Babbage's new machine for calculating and printing mathematical and astronomical tables.pdf/2

411 computations. The best proof of their utility and convenience is the immense variety that has been produced since the origin of printing; and the diversity of those which are annually iſsuing from the preſs.

The general tables, formed for the purpose of assisting us in our computations, may be divided into two classes: 1o. those consisting of natural numbers: 2o. those consisting of logarithms. Of the former kind are the tables of the products and powers of numbers, of the reciprocals of numbers, of the natural sines, cosines etc. etc. Of the latter kind are not only the usual logarithmic tables, whose utility and importance are so well known and duly appreciated, but also various other tables for facilitating the several calculations which are constantly required in mathematical and physical investigations. I shall allude to each of these in their order.

1o. Tables of the products of numbers. The numerous tables of this species which have been published at various time, and in different countries, sufficiently attest their utility and importance: and there can be no doubt that, if their accuracy were undeniable, their employment would be much more frequent. One of the first tables of this claſs was published in „Dodson's Calculator“; and contains a table of the first nine multiples of all numbers from 1 to 1000. In 1775 this table was much extended, and printed in an octavo size: it comprehended the first nine multiples of all numbers from 1 to 10000. Notwithstanding these and other tables of the same kind, the Board of Longitude considered that still more extended tables might be useful to science, and employed the late Dr. Hutton to form a multiplication table of all numbers from 1 to 1000, multiplied by all numbers leſs than 100. These were printed by their directions; and it is to be presumed that no expense was spared to render them accurate: yet in one page only of those tables (page 20) no leſs than forty errors occur, not one of which is noticed in the printed list of the errata. The French government, likewise, sensible of the utility of such tables, order the construction of a still more extensive set for the use of several of its departments. These are comprised in one volume quarto, and extend from the multiplication of 1 by 1 to 500 to 500: and in the year 1812, they caused a second edition of those tables to be printed. But, the most convenient tables of this kind which have yet appeared were recently published at Berlin, by M. Crelle; and comprise, in one octavo volume, double the quantity of the French tables. Another volume, of the same size, which is announced by the same author, will render these by far the most valuable of their kind, provided their accuracy can be relied on. The quantity of mental labour saved, in the construction of such tables, by the help of the machine, is literally infinite: for, in fact, no previous calculation is at all requisite; and it will be necessary merely to put into the machine, at the end of every two pages, the number whose multiples are required. This number will be successively 1, 2, 3 etc… to 500.

2o. Tables of Square Numbers. The squares of all numbers, as far as 1000, were a long time ago published on the continent by M. Lambert. These have been since extended as far as the square of 10000 by Mr. Barlow of the Royal Military Academy at Woolwich. The Board of Longitude employed the late Dr. Hutton to calculate a similar table as far as the square 25400. In computing a table of this kind by the machine, even if extended to the most remote point that could be desired, the whole of the mental labour would be saved: and when the numbers 1, 1, 2 are once placed in it, it will continue to produce all the square numbers in succession without interruption. This is, in fact, one of those tables which the engine already made is capable of computing, as far as its limited number of wheels will admit.

3o. Tables of Cube Numbers. Tables of this kind have likewise been already computed by Mr. Lambert and Mr. Barlow; and also by the late Dr. Hutton, by order of the Board of Longitude. In computing such a table by the machine, the whole of the mental labour would be in this case also saved: since it would be merely necessary to place in the machine the numbers 1, 7, 6, 6; and it would then produce in succession all the cube numbers.

4o. Tables of the higher Powers of Numbers. The Board of Longitude employed Dr. Hutton also to construct a limited table of this kind; which should contain the first ten powers of all numbers from 1 to 100. And Mr. Barlow has published, in his collection, a table of the fourth and fifth powers of numbers between 100 and 1000. Should it be thought desireable to re-compute or extend these tables, the whole labour may be performed by the help of the machine, except the few figures required to be first placed in it; and which might perhaps occupy the computer about ten minutes for each power. In fact the computation of these few fundamental figures would not occupy so much time, nor be so liable to error, as the calculation of one of the tabular numbers, according to the usual method.