BoO't t. LAMB. 225 �The state of the art of making tubes, or pipes of Eheet metal, ^as some what different. They were not made in a spiral'f orm, though straight pipes were joined by a folded seam like tiiat of Eitchie. �In thia state of the two arts, the specification of Eoot ap- pears to be addressed to persons who are acquainted with spiral tubes. He does not tell how to make them, but how to make the skelp from which they are to be made. I under- stand that the difficulty in making the Eitchie pipe is not ih making the strip, but in winding it up spirally so a.s at the same time to' make a folded seam. �There are many reasohsfor saying that Eoot's specification does not, updn its face, appear to refer to that sort' of metal used by tinsmiths. The fact that it was not intended to refer to them would not have been admissible, but for certain inadmissible stateihents of the plaintiff. The words, as con- strued in view of the art, are the important things. The Word "skelp" is never used in the art of the tinsmith, and Eitchie's strip of sheet metal is not a skelp. To be sure, a patentee may misuse a word, but when we are seeking for his meaning, the ordinary signification of the words which he uses must have its weight. He speaks of the heated skelp and the saving of fuel, and of other things applicable to tubes of a certain class, and not applicable to the Eitchie tube. It is said that some of these words and phrases are not found in the modification. This is true; but no new process is referred to or hinted at in that clause. It is merely to save repetition that the phrases are left out. The skelp referred to is the same sort of skelp, excepting in the form of the ridges and furrows, ^nd they are intended to be rolled upon the heated skelp. The brevity of the clause is strong evidence that it does not refer to a different subject. �If the patentee had suggested ' that a pipe or tube of sheet metal might be made by winding it spirally with a folded seam, it is very doubtful whether he could have patented that pipe Without showing the world how to make it. I do not under- stand it to be serioualy contended on his behalf that the Eitchie pipe could be made by following his specification. He �v.7,no.2— 15 ��� �
