=Saccardo’s System.=--A new method of ventilating tunnels was devised by Mr. Saccardo for the ventilation of the Pracchia tunnel along the Bologna and Lucca Railway in Italy. At the highest end of the tunnel the mouth was contracted inward in a funnel shaped form so as to just admit a train. Immediately at this contraction, a lateral tunnel, 50 feet long, branched off from one side of the main tunnel. At the mouth of this lateral tunnel was installed a fan which forced air into the tunnel and with 70 revolutions per minute delivered 3.532 cu. ft. of air per second at a water pressure of 1 in. This air current was directed inward through a second contraction or funnel, parallel to the one at the entrance and 23 ft. beyond it. In operation the action of the artificial air current was to suck in a considerable volume of outside air, while the air pressure was sufficient to counterbalance the movement of air produced by a train moving at a velocity of 16.1 ft. per second. Mr. Saccardo’s method was employed in ventilating a tunnel on the Norfolk and Western Railway with satisfactory results. =Compressed Air.=--In the excavation of tunnels in hard rock a number of rock drilling machines are employed which are moved by compressed air at a pressure of not less than five atmospheres. At each stroke about 100 cu. ins. of compressed air are set free, and at an average of 10 strokes per minute there would be 5000 cu. ins. of air at five atmospheres or 25,000 cu. ins., or a little more than 175 cu. ft. of fresh air at normal pressure set free every minute by each of the machines employed. But the air exhausted from the drilling machine is foul. Regarding ventilation by compressed air, Mr. Adolph Sutro, in a lecture delivered to the mining students of the University of California, said: “I will note a curious fact which I have never seen explained, and which is worthy of close investigation by means of experiments. In the Sutro tunnel we found that the compressed air used for driving the machine drills, after having been compressed and expanded and discharged from the drills, was not wholesome to breathe, and the men and mules would all crowd around the end of the blower pipe to get fresh air. Whether the air in being compressed has parted with some of its oxygen or because vitiated from some other cause, I do not know, and I hope that this subject will at some future day be carefully examined into.” In the December, 1901, number of “_Compressed Air_,” a magazine especially devoted to the useful application of compressed air, is read: Compressed air wasted from power drills is so contaminated with oil from the cylinders that it cannot be taken into consideration as ventilation. It is as important to displace it with pure air as it is to drive out or draw off other vitiated air. The ventilation should be an independent supply provided by fan or blower, delivering by pipe at the point where miners are working.