416. The effects of regulations of excise upon our home manufactures are often productive of great inconvenience; and check, materially, the natural progress of improvement. It is frequently necessary, for the purposes of revenue, to oblige manufacturers to take out a license, and to compel them to work according to certain rules, and to make certain stated quantities at each operation. When these quantities are large, as in general they are, they deter manufacturers from making experiments, and thus impede improvements both in the mode of conducting the processes and in the introduction of new materials. Difficulties of this nature have occurred in experimenting upon glass for optical purposes; but in this case, permission has been obtained by fit persons to make experiments, without the interference of the excise. It ought, however, to be remembered, that such permission, if frequently or indiscriminately granted, might be abused: the greatest protection against such an abuse will be found, in bringing the force of public opinion to bear upon scientific men and thus enabling the proper authorities, although themselves but moderately conversant with science, to judge of the propriety of the permission, from the public character of the applicant. 417. From the evidence given, in 1808, before the Committee of the House of Commons, On Distillation from Sugar and Molasses, it appeared that, by a different mode of working from that prescribed by the Excise, the spirits from a given weight of corn, which then produced eighteen gallons, might easily have been increased to twenty gallons. Nothing more is required for this purpose, than to make what is called the wash weaker, the consequence of which is, that fermentation goes on to a greater extent. It was stated, however, that such a deviation would render the collection of the duty liable to great difficulties; and that it would not benefit the distiller much, since his price was enhanced to the customer by any increase of expense in the fabrication. Here then is a case in which a quantity, amounting to one-ninth of the total produce, is actually lost to the country. A similar effect arises in the coal trade, from the effect of a duty, for, according to the evidence before the House of Commons, it appears that a considerable quantity of the very best coal is actually wasted. The extent of this waste is very various in different mines; but in some cases it amounts to one-third.