424. The restriction of articles produced in a manufactory to certain sizes, is attended with some good effect in an economical view, arising chiefly from the smaller number of different tools required in making them, as well as from less frequent change in the adjustment of those tools. A similar source of economy is employed in the Navy: by having ships divided into a certain number of classes, each of which comprises vessels of the same dimensions, the rigging made for one vessel will fit any other of its class; a circumstance which renders the supply of distant stations more easy. 425. The effects of the removal of a monopoly are often very important, and they were perhaps never more remarkable than in the bobbin net trade, in the years 1824 and 1825. These effects were, however, considerably enhanced by the general rage for speculation which was so prevalent during that singular period. One of the patents of Mr Heathcote for a bobbin net machine had just then expired, whilst another, for an improvement in a particular part of such machines, called a turn again, had yet a few years to run. Many licenses had been granted to use the former patent, which were charged at the rate of about five pounds per annum for each quarter of a yard in width, so that what is termed a six-quarter frame (which makes bobbin net a yard and a half wide) paid thirty pounds a year. The second patent was ultimately abandoned in August, 1823, infringements of it having taken place. It was not surprising that, on the removal of the monopoly arising from this patent, a multitude of persons became desirous of embarking in a trade which had hitherto yielded a very large profit. The bobbin net machine occupies little space; and is, from that circumstance, well adapted for a domestic manufacture. The machines which already existed, were principally in the hands of the manufacturers; but, a kind of mania for obtaining them seized on persons of all descriptions, who could raise a small capital; and, under its influence, butchers, bakers, small farmers, publicans, gentlemen's servants, and, in some cases, even clergymen, became anxious to possess bobbin net machines.