Scottish Court of Session Decisions

In this case, Alexander M'Dougall, manufacturing chemist, Manchester, was pursuer and Robert Girdwood, wool-broker, Tanfield, Ediburgh, was defender. The pursuer set forth that, by letters-patent, he had obtained for fourteen years the exclusive privilege of making and vending his invention within the United Kingdom. In his specification he claimed, as secured to him by the letters-patent,—1st, The use of carbolic acid in the preparation of materials or compositions for destroying vermin on sheep and other animals, and for protecting them therefrom; 2d, The use of alkalies and tallow, or other saponifiable substance, in combination with the above products, when used for the purposes set forth. In his subsequent disclaimer and memorandum of alteration, the pursuer declared—“My invention consists in the use of the heavy oil of tar, or dead oil, or crude carbolic acid, as it is sometimes called, or creosote obtained in the destructive distillation of carbonaceous substances. These materials I treat with an alkali, and add a saponifiable fatty substance.” The issues tried before the Lord President and a jury in April last, were—1. “Whether, between 28th January 17th May 1866, the defender did, within or near his premises at Tanfield, near Edinburgh, wrongfully, and in contravention of the said letters-patent, use the invention described in the said specification, as altered as aforesaid?” 2. “Whether, between 28th January and 17th May 1866, the defender did, wrongfully, and in contravention of the said letters-patent, vend a material for destroying vermin on sheep and other animals, and for protecting them therefrom, manufactured by the use of the invention in the said specification, as altered as aforesaid?”

The defender denied that the “Improved Melossoon or Sheep Protecting Dip” sold by him was the same, or substantially the same, as the pursuer's invention, and explained that he used in his manufacture light pitch oil, having a less specific gravity and a lower boiling point than water, and also vegetable poisons; heavy oil of tar, or dead oil, or crude carbolic acid, or creosote, being carefully excluded, as being injurious to the wool. A number of scientific witnesses were examined. The jury returned a verdict for the pursuer. The defender now presented a bill of exceptions to the Judge's charge, in so far as he had left it to the jury to say, on the evidence, whether the words in the specification, “the heavy oil of tar,” &c., do, in their ordinary meaning, as known in trade, comprehend oils produced from the destructive distillation of coal tar, of a specific gravity less than the specific gravity of water; and, particularly, the oil used by the defenders in the manufacture of the composition complained of, as a contravention of the patent; and had directed them in law, that they must find for the defender if they should be of opinion that the said words did not comprehend such oils. The defender also asked the Judge to direct the jury (1) that, according to the true construction of the letters-patent, specification, and disclaimer, no oil of a less specific gravity than water is comprehended within the said patent, specification, and disclaimer; (2) that if the tar oil used by the defender was, prior to the date of the patent, commercially known and used, and was of a lighter specific gravity than water, the pursuer was not entitled to a verdict on either issue. The Judge refused to give these directions.

A hearing took place on the bill of exceptions and also on a rule, obtained by the defender on the pursuer, to show cause why the verdict should not be set aside as against evidence.

Young, Mackenzie, and Balfour for pursuer.

Clark, Watson, and R. V. Campbell for defender.