Where one, in the preservation of his own property or the promotion of his own interests, does something which is of incidental advantage to another, there is no obligation to pay the value of such advantage. Even if the person conferring the benefit supposes that he will be entitled to compensation, he can hardly be said to confer it in reliance upon such supposed right. It has accordingly been held that the United States could not recover from a railroad company the value of its services in rebuilding the railroad company's bridges, the work having been done as a military necessity;2 that the owner of the lower part of a house was not liable for the advantage resulting to him from the repair of the roof by the owner of the upper part and roof;3 that one who thickened and strengthened that part of an ancient party wall which was on his own land, in order to sustain a building he was erecting, was not entitled to recover from the owner of the adjoining property who subsequently used such strengthened wall;4 that nothing could be recovered from the owner of a vessel by the underwriters who had her docked for the purpose of making necessary average repairs, although the dock-ing of the vessel enabled the owner to make a survey required for the retention of her classification;5 that one who in pumping out his own quarry incidentally freed another's quarry from an accumulation of water could not recover for such service;1 that one who was benefited by experiments made by another to test the value of certain patented inventions in which both are interested was under no obligation to pay for such benefit.2

1 See Hudson v. Hudson, 1891, 87 Ga. 678; 13 S. E. 583; 27 Am. St. Rep. 270, which, however, was a case of impossibility of performance by the defendant, a topic to be treated later. See post, Sec. 127.

2 United States v. Pacific R. Co., 1887, 120 U. S. 227; 7 S. Ct. 490.

3 Loring v. Bacon, 1808, 4 Mass. 575.

4 Walker v. Stetson, 1894, 162 Mass. 86; 38 N. E. 18; 44 Am. St. Rep. 350. For an interesting note on this case, see 8 Harv. Law Rev.

171.

5 Ruabon Steamship Co. v. London Assurance, [1900] A.C.6 cf Marine Ins. Co. v. China, etc., Co., 1886, 11 A. C. 573.