IN Paris, a municipal regulation requires the periodical cleaning of the house-fronts; and a due regard to the appearance of the buildings, from the street would suggest a similar practice in many cities on this side of the water. The plan most approved in Paris, where it has been in use for the past two years, is to throw against the house-front a jet of water forcibly projected by steam pressure. The advantages of this mode are cheapness, the avoidance of injury to the more fragile ornamental or sculptural portions of the building, and universality of application. Aside from the cleanly and fresh appearance of the houses secured by thus washing the fronts, other desirable results may be in a measure secured; thus, for instance, it has been calculated that if the exterior walls of all the buildings in London were kept clean, instead of being grimy and nearly black from top to bottom, a gain of half an hour of daylight in every twenty-four hours would be obtained.