Dry powder fire extinguishers were much advertised at one time, but in a presidential address recently delivered before the American society of Mechanical Engineers, Mr. John R. Freeman said that the chief reason why these long tin tubes of powder have become popular is that they can be manufactured for about 10 cents each, and that they retail as high as $3 each. They are nearly all composed of common bicarbonate of soda, frequently disguised by the admixture of a cheap coloring matter, like Venetian red, and prevented from caking by the addition of starch. Samples of everything of this kind that Mr. Freeman could find were purchased in the ordinary channels of trade by different parties, and the respective groups of samples were analyzed by three different chemists in order to fortify Mr. Freeman against the possibility of wronging anyone through a mistake in the analyses, and had samples sealed up and retained for further analyses should anyone question his figures. Mr. Freeman had tests made of several of them and found them of doubtful value on even the smallest fires, and worthless for a fire in free ventilation. Generally considered, he would recommend throwing them into the rubbish heap. Pails of water are, in his opinion, far more reliable.