The patent involved in filis ease was so thoroughly discussed in Judge Avis’ opinion that we find ourselves in no position to improve on what he has said. After due consideration, we are of opinion the decree below should be affirmed, and affirmed on Ms opinion. In so doing, we note that this patent presents an unusual state of affairs.

What was known as the “cotton” knitting machine had been in use for many years. Its construction involved some one hundred patents. The machine cost $.10,000'. The plaintiff devised a mere attachment, costing some £350, which can be attached to the $10,000 naehine, a.nd gives the latter a wide sphere .if manufacturing capacity which it did not eefore possess. This attachment was so valuable — and there is no contradiction as to this — that no one would now buy one of these $10',000 machines without having an attachment such as the plaintiff’s patent disclosed. Its worth is evidenced by the fact that in four years following the issue of the patent 6,000 of these attachments were sold at a cost of more than $2,000,000. When this patent was disclosed to the plaintiff, an extensive manufacturer of knitting machines, the patentee was at once paid $20,0*00' for it. We have a finding by the Patent Office of the fact of invention. We also have tfie fact of invention found by the trial court. We see no reason to disturb such findings. Accordingly, the case is affirmed.