163. The economical principles which regulate the application of machinery, and which govern the interior of all our great factories, are quite as essential to the prosperity of a great commercial country, as are those mechanical principles, the operation of which has been illustrated in the preceding section. The first object of every person who attempts to make any article of consumption, is, or ought to be, to produce it in a perfect form; but in order to secure to himself the greatest and most permanent profit, he must endeavour, by every means in his power, to render the new luxury or want which he has created, cheap to those who consume it. The larger number of purchasers thus obtained will, in some measure, secure him from the caprices of fashion, whilst it furnishes a far greater amount of profit, although the contribution of each individual is diminished. The importance of collecting data, for the purpose of enabling the manufacturer to ascertain how many additional customers he will acquire by a given reduction in the price of the article he makes, cannot be too strongly pressed upon the attention of those who employ themselves in statistical enquiries. In some ranks of society, no diminution of price can bring forward a great additional number of customers; whilst, amongst other classes, a very small reduction will so enlarge the sale, as to yield a considerable increase of profit. Materials calculated to assist in forming a table of the numbers of persons who possess incomes of different amount, occur in the 14th Report of the Commissioners of Revenue Inquiry, which includes a statement of the amount of personal property proved at the legacy office during one year; the number of the various classes of testators; and an account of the number of persons receiving dividends from funded property, distributed into classes. Such a table, formed even approximately, and exhibited in the form of a curve, might be of service.