THATCHER HEATIMG 00. V. SPEAE. 4:11 �less presBure may be brought to bear upon the defendants^ Bpring than upon the plaintiff's, and it may be less liable to injury. �The law upon the aubject of equivalents for one of the members of a combination of old ingredients bas been fre- quently laid down of late by the supreme court. It is stated in GUI V. Wells, 22 Wall. 1, as foUows : "By an equivalent in suoh a case it is meant that the ingredient substituted for the one withdrawn performs the same function as the other, and that it was well known, at the date of the patent securing the invention, as a proper substitute for the one omitted in the patented combination. Hence it follows that a party who merely substitutes another old ingredient for one of the in- gredients of a patented combination is an infringer, if the substitute performs the same function as the ingredient for ■which it was substituted, and was well known at the date of the patent as a proper substitute for the missing ingredient. But the rule is otherwise if the ingredient substituted was a new one, or performed substantially a different function, or was not known at the date of the plaintiff's patent as a proper substitute for the one omitted, as in that event he does not infringe. " �There must be a decree for an injunction, and for an ac- couuting in regard to ail articles made like Exhibit e, with costa. ���The Thatcher Hbating CoMPAïnr v. Spbar and another. �(tlrcuit Court, 8. D. New Yfrrk. January 28, 1880.) Patent— Improvements iîi AïK-HBATiNa FuiwfA«HB. �Infringement of Patent. �B. F. Lee, for plaintifE. �E. Cowen, for defendants. �Blatchfobd, J, Thig suit is founded on letters patent No. 71,24e, granted to John M. Thatcher, November 19, 1867, for an "air-heating furnace." The specification states that ��� �
