The witness is complainant’s expert, who is being cross-examined on the prima facie; and the question relates to one of many patents set up in the answer, either as anticipations, or as showing a state of the art which calls for a narrow construction of the patents sued upon, or possibly for a decision adverse to complainant on the question of invention. Objection is taken that this is not proper cross-examination, since the prior patent was not referred to on the direct. Where the direct examination of an expert on prima facie is confined to its proper limits, viz. a description of the patent, explaining whatever obscurities it may-present to the mind not skilled in the art, and defining its technical terms, supplemented by a presentation of the infringing device and an explanation of whatever features of it are covered by the claims, then it is not logical or proper to open up the state of the art relied upon in defense through cross-examination of complainant’s witness. It is defendant’s expert who should introduce that branch of the case. In this case, however, complainant’s expert has not so confined himself. He has referred to the state of the art, briefly, it is true, but nevertheless sufficiently, in order to magnify the meritoriousness of the invention; and therefore defendants are within their rights in insisting upon a cross-examination covering the whole state oí the art. If £he direct examination is to stand as it is, the objections to cross questions 300 and 301 are overruled. If complainant, however, is willing to pay the stenographer’s fees for taking so much of the cross-examination as deals with the prior art, — a cross-examination induced by the witness’ direct testimony, — he may strike out all the direct testimony of his expert, except such as qualifies him, down to and including the long quotation from Judge Townsend’s opinion on page 10, and all of the cross which deals with the prior state of the art, and the objections will then be sustained.