The greatest mass of legislation is, of course, that upon mechanic's liens, which are burdensome to a degree that is vexatious, besides being subject to amendment almost every year. In a general way, no land-owner is free from liability for the debt of any person who has performed labor or furnished materials on the buildings placed upon the land, even without the knowledge or consent of the land-owner in some States, though in one or two instances, notably in California, such legislation has been carried to such an extreme as to make it unconstitutional. The matter of nuisances has been already somewhat covered. Legislation extending the police power and declaring new forms or uses of property to be a nuisance is, of course, rapidly increasing in all States. The common-law nuisance was usually a nuisance to the sense of smell or a danger to life, as, for instance, an unsanitary building or drain. Noise, that is to say, extreme noise, might also be a nuisance, and in England the interference with a man's right to light and air. Legislation is now eagerly desired in many States of this country to make in certain cases that which is a nuisance to the sense of sight also a legal nuisance, as, for instance, the posting of offensive bills on the fences, or the erection of huge advertising signs in parks or public highways. Such a law was, however, held unconstitutional in Massachusetts. There is some legislation against the blowing of steam whistles by locomotives, although I believe none against the morning whistle of factories, and some against the emission of black smoke in specified durations or quantities.