that it was like the action of a windmill with reference to the wind. That reasoning, however, did not succeed." (Dangerfield v. Jones, 13 L. T. N. s. 142.)

It must be carefully kept in mind, that unless there is some display of ingenuity, a patent for the application of an old contrivance to a new object will not be valid. But it is impossible to lay down any general rule as to the amount of ingenuity which is essential to support a patent. In nice cases, there can be no certainty previous to a judicial decision on the point whether any given patent is or is not impeachable on the ground of want of ingenuity; which phrase cannot be regarded, perhaps, as different from want of novelty. All that can be done is to study the decisions already made, and to be guided by those cases which approach nearest to the one about which doubt may be felt. Some of the decisions, indeed, seem to conflict with others; and it will require a good deal of acute discrimination on the part of those who are called on to advise inventors, to distinguish the line which separates what is patentable from what is not patentable. In the case of Kay v. Marshall, Lord Cottenham said, in the House of Lords, " that if Kay had discovered any means of using the machine (i.e. the ordinary spinning machine) which the world had not known before, the benefit of that he had a right to secure to himself by means of a patent; but if this mode of using the spinning machine was known before, then he could not deprive them of having the benefit of that which they enjoyed before" (2 W. P. C. 82). The reader will see how nearly such a proposition conflicts with the case of Bush v. Fox (Macr. P. C. 152).

5. A mode of manufacturing differing in nothing from an old process, except in the omission of a step, may also form the subject of a patent, as was decided in the case of Russell v. Cowley (1 W. P. C. 459). A patent had

been obtained for an invention for manufacturing iron tubes, by welding them without the use of a mandril, or internal support; and its validity being contested, it was held good. The process, from first to last, consisted in turning up the edges of a flattened metal plate until they nearly met; in heating the plate, so prepared; and in drawing it when at a welding heat through dies having a conical hole. In passing from the broader to the narrower end of the hole, the edges were compressed against each other, and were welded together; the tube was thus formed without having recourse to the old process, which required a mandril, whereon the overlapping edges of the metal plate were welded by means of hammers. It being contended that welding by pressure was not a new invention, Lord Lyndhurst read the specification as claiming only the manufacture of tubes without a mandril. By the new process, tubes could be made of greater length, of greater uniformity, and considerably cheaper, than before.

It was held in Booth v. Kennard (1 H. & N. 527), that to obtain gas by the direct distillation of oleaginous seeds was a patentable invention, although gas had been previously obtained by the distillation of oil expressed from oleaginous seeds.

6. Chemical processes, usually but not always in combination with mechanical contrivances, whereby something useful is produced or effected. Under this head the following examples may be given: the purification of coal gas by means of oxides, chlorides, &c. (Hills v. London Gas Company, 5 H. & N. 312); the precipitation of the solid animal and vegetable matter contained in sewage water with a view to its employment as manure (Higgs v. Goodwin, E. B. & E. 529); the preparation of dyeing materials (Steiner v. Heald, 6 Exch. 607; Simpson v. Holliday, 5 N. R. 340, L. R. 1 H. L. 315); the mixture of two or more sub

stances in certain definite proportions forming a compound substance useful for its preservative, medicinal, or other qualities (Muntz v. Foster, 2 W. P. C. 103; Bewley v. Hancock, 6 De G. M. & G. 402).

AMOUNT OF INVENTION REQUIRED TO SUPPORT A PATENT.

In contesting the validity of a patent, it is often objected that there had been no exercise of ingenuity on the part of the alleged inventor in arriving at his invention, and that mere accident or good luck is not entitled to a patent privilege. Where, however, the utility of the invention is great, and the novelty undoubted, these facts will come in aid of an apparent want of ingenuity on the part of the inventor. "In point of law" (said C. J. Tindal, in Crane v. Price, 1 W. P. C. 411), "the labour of thought or experiment, and the expenditure of money, are not the essential grounds of consideration on which the question whether the invention is or is not the subject-matter of a patent ought to depend; for if the invention be new and useful to the public, it is not material whether it be the result of long experiment and profound search, or whether by some sudden and lucky thought, or mere accidental discovery." In either of the two last cases, the practical realization of a good idea must be considered a sufficiently meritorious consideration for the exclusive privilege granted to the inventor, although the actual amount of thought expended in making the invention is trifling. The case of watertabbies, so often mentioned in Westminster Hall, is a case in point. The invention (according to Mr. Justice Buller, in Boulton v. Bull, 2 H. Bl. 463, 1 Carp. 117) first owed its rise to the accident of a man spitting on a floor-cloth, which changed its colour, whence he reasoned, had his patent, and made, it is said, a considerable fortune by it.

The making of iron gas-tubes without the use of a mandril, viz. by welding them without striking them on a solid surface, "seems to be a very simple invention" (said Lyndhurst, C. B., in Russell v. Cowley); "but it has been productive of great advantages, inasmuch as it has enabled the manufacturer to construct pipes of lengths much beyond what could be done previously to this discovery" (1 W. P. C. 467). Hence the utility of the invention was apparent from the important consequences that flowed from it, and the patent was supported.

The case of Lewis v. Davis (1 W. P. C. 488) is usually cited to show that a small degree of invention suffices to sustain a patent, provided it be attended with useful results. The object of the patent was the shearing of cloth from list to list by means of rotatory cutters. Now a rotatory cutter to shear from end to end was known, and cutting from list to list by means of shears was also known. "However" (said Tenterden, C. J., to the jury, on the trial of an action for the infringement of the patent, in which the question of novelty was raised), "if before the plaintiffs' patent the cutting from list to list, and the doing that by means of rotatory cutters, were not combined, I am of opinion that this is such an invention by the plaintiffs as will entitle them to maintain the present action."

In the case of Hinks v. Safety Lighting Company (L. R. 4 Ch. D. 607), Sir George Jessel, M. R., held that the substitution of a flat wick for a solid round wick in a lamp was a sufficient ground for a patent; because, notwithstanding the apparent smallness of the invention, it had the effect of largely increasing the illuminating power of the lamp, in other words, it

was a very useful invention. In giving judgment in the plaintiff's favour the learned Judge made the following remark:-"Where a slight alteration in a com

bination turns that which was practically useless before into that which is very useful and very important, judges have considered that though the invention was small yet the result was so great as fairly to be the subject of a patent; and as far as a rough test goes, I know of no better." See also Frearson v. Loe (L. R. 9 Ch. D. 48).

With these cases compare that of Patterson v. The Gas Light and Coke Company (L. R. 2 Ch. D. 812, affirmed on appeal L. R. 3 App. Cas. 239). Here a patentee claimed the employment of sulphides of calcium in separate purifiers as a means of purifying coal gas from sulphur existing in other forms than that of sulphuretted hydrogen. Now, as it was well known to chemists, and had been long taught in books, that sulphides of calcium would absorb sulphur compounds -moreover, as it was plain that if sulphide of calcium was to be used, a separate holder must be employed, and as no special apparatus was suggested, it was held that there was no invention that would support a patent. The same patentee also claimed a method or system of employing lime purifiers in succession, whereby the contents of all the purifiers, or any required number of them, could be converted into sulphides of calcium, and also, if required, be maintained in that condition. Now, lime purifiers in succession had been in general use for a long time, and the patentee had not devised either a new process or any new apparatus. What he really thought he had discovered was that, if the carbonic acid, which is the first thing taken up by the lime, was allowed to enter the last purifiers, it would have a deleterious effect on the purifying process. It ought, therefore, to be removed at the beginning of the operation. But this, though it might be a very useful piece of advice, and an instruction of great value, was held by the Court