The excessive expence of insurance, arising from the numerous candles employed in most of the first-rate manufacturing establishments, and the combustible nature of the structure of the buildings; the great difficulty of retrieving the injury resulting to a well-organised business, from the accidental destruction of the machinery, are considerations alone sufficient to furnish the strongest economical, as well as political recommendations, for the adoption of the new lights in all manufactories where work is done by candle-light. We have as yet only adverted to the application of gas in the more ordinary cases where light is wanted, but among other special purposes to which gas-lights may be applied, it would be improper to overlook the peculiarly advantageous use which may be made of them in the supplying of light-houses. From the splendour and distinguishing forms which the gas-light flame is capable of assuming, nothing can possibly be better calculated for such a purpose; and in point of economy, the employment of it would be attended with a saving of at least one half of the ordinary expence of oil lights. By means of a single furnace, as much gas may be produced in three hours, as will furnish during the longest winter night, a flame of greater brilliancy than is now furnished by any lighthouse in Britain, or indeed in the world. The body of flame may be increased to any size, merely by increasing the number of burners; and whatever may be the magnitude of the flame, it will continue to burn, without becoming in the least clouded by smoke, or the reflectors being in the least obscured. Should these considerations lead, as it is to be hoped they will, to the actual employment of gas in the lighthouses around the British islands, it will readily occur, that in proportion as the gas would be found attended with less expense than the present mode of lighting by oil, it would enable the commissioners for light-houses, out of the surplus means which would be thus placed at their disposal, to multiply the number of lighthouses, and thus to add most essentially to the security of British navigation. Nor is it in the case of maritime signal-lights alone, that the use of gas is applicable, by its superior efficacy and cheapness. The saving of expences to the country which would be effected by the substitution of coal gas, for oil and tallow in these and other public establishments, is a consideration which cannot be too much pressed on public attention. The annual expenditure for lighting the barracks of Great Britain alone, is said to fall little short of fifty thousand pounds; for less than one half of which sum, they might be lighted by means of gas much better, and a great deal more safely. Some idea may be formed from the practical saving in this department--how great might be the total saving, were this new mode of lighting adopted in all our national establishments.