Herein lies the immense and irreconcilable difference between property in land and that of invention. Besides, land cannot become unfertile, unproductive, or lose all its value as property, except by some convulsion of nature which would deeply unsettle it. An invention, on the contrary, may become quite valueless in ten years, one year, a fortnight even, after being discovered, and that by the superiority of a subsequent invention. What becomes, then, of the property of this invention? What is its worth? Has the inventor a right to damages? If you construct near my field a factory from which escape noxious vapours, hurtful to vegetation, and if I can show that you have deteriorated or destroyed my crops, you, according to the laws of every civilised nation, owe me damages; would you claim damages of the inventor, whose discovery had rendered that of one of his predecessors partially or completely unproductive? If property in invention is equal to property in the soil, damages are incontestably due. We do not think that a single advocate for this class of property has, however, dared to carry his logic thus far. The proprietor of a field may leave it uncultivated, the proprietor of a house may leave it shut up as long as he likes; no law obliges to put in a tenant, or to open it for lodgers. The laws of all countries contain, with slight modifications, the following clause, quoted from Art. 32 of the Law of 1844:—“Will be deprived of all his rights ... the patentee who shall not have commenced the working of his discovery or invention in France within two years, dating from the day of the signature of the Patent, or who shall have ceased working it during two consecutive years, unless that, in one or other case, he can satisfactorily explain the causes of his inaction.” It would be very easy for us to cite other differences in the nature of these two classes of property; we shall only refer to one more, which points out how solid is the property in land, and how uncertain and ephemeral the so-called property of invention. Land, considered as property, increases in value from day to day; there is no invention whose value does not diminish daily.