and a large population are in reality due to the greater contamination of the air we breathe by the waste products of that population, and that toxines excreted by the lungs will in time take high rank among these as both potent and insidious. If this should come to pass, the present ideas anent ventilation must be abandoned as utterly futile, and the need will be felt, not of letting a little air in, but of letting waste products out. =The Utilization of Wave Power.=--The utilization of the energy which goes to waste in the movement of water, in waves, tides, and waterfalls, has been a much-studied problem during recent years. The only one of these three phenomena which has as yet been at all extensively commercially harnessed is the waterfall. There have, however, been a number of wave and tide motors constructed. The most recent and perhaps the most promising of these is the type invented by Mr. Morley Fletcher, of Westminster, England. He has made a special study of the problem of motion of the sea, and has already successfully constructed a hydraulic pump, an electric motor, and a self contained siren buoy in which the energy is obtained entirely from wave motion. The great possibilities in this direction for cheap and efficient power plants have not been appreciated by seacoast towns, but it is stated in Industries and Iron, from which we have taken the above particulars, that Mr. Fletcher is at present devoting his attention to devising schemes and designing apparatus for pumping sea water for shore purposes, ore washing, driving electric machinery for town lighting and power plants, buoys for marking harbors with beacons and fog horns, and the many other purposes to which such a constant and inexhaustible source of energy is applicable.