The President. especially qualified to speak on the subject of the prevention of pollution by trades waste, because his professional avocations brought under his inspection a great many manufactories. But however desirable it was to prevent the pollution of streams, it was necessary to be careful not to harass the manufacturers to such an extent as to ruin their trade. Manufacturers often had but a small margin of profit, and were in competition with foreigners who were not subject to the restrictions which obtained in England. Happily the utilization of trades waste sometimes led to profit. An admirable instance of the profits arising from trades waste might be found in gasworks. I n former days the tar and ammoniacal liquors had been got rid of as best they might be, with no thought of utilizing them. Now those refuse products were a great aid in lowering the price of gas.