Lord Merrivale.—

The appellants, the United States Shipping Board, are owners of the "Crown City," a steel screw motorship of 5,428 tons gross register, and 426 feet in length, which on 22nd October 1927, found herself in collision with the defendant's steel single screw steamship "St. Albans," a vessel of 4 119 tons gross register and 367 feet in length, in Sydney Harbour near to Bradley Head, where is found the turning point and place of passing of the traffic into and out of the harbour. The "Crown City" was outward bound for Melbourne from Wooloomooloo Bay within the harbour. The "St. Albans" was inward bound from Japan.

In its actual incidents the collision, which took place in broad daylight, was of an ordinary kind involving simple questions to be determined upon the usual conflict of evidence as to the exact place of the casualty and the course and management of the ships. The proceedings in the litigation have been of an unusual kind. Under the provisions of the law locally applicable a Commonwealth Court of Inquiry was held, presently after the collision, whereat both parties now in litigation were represented by counsel. Following on the inquiry the now appellants brought their action in the Supreme Court of New South Wales (in Admiralty) alleging the respondents by their servants to have been to blame for the collision. After preliminary acts bad been filed the parties agreed that the action should be tried on the evidence given at the inquiry. Respondents however called at the hearing before the Chief Justice of New South Wales a surveyor to explain certain photographs, hereafter mentioned at length, which had been produced by one of the witnesses at the inquiry. Then the troubles of the parties as to procedure commenced.

Before the Court of appeal the respondents obtained leave to call further evidence, and in fact called three land surveyors who gave evidence which they stated to be proof of facts demonstrated by or demonstrable upon the photographs. On the strength of this additional testimony, the finding of the trial Judge in favour of the appellants was reversed. What is mainly in question here is the admissibility of this evidence, and if it be received, its proper effect in the determination of the question of liability for the collision. The nature of the additional proof received in the Court of appeal and its value as evidence raise questions of law and practice of some general importance.

To make the main facts of the collision intelligible the courses of the two ships need to be appreciated. The usual course of an outward bound vessel, upon rounding Garden Island, which lies eastward of Wooloomooloo Bay, is to get upon a heading of 95°-that is E. 5° S.-and on that course to proceed across the harbour until Bradley Head Lighthouse is about abeam, and then under a starboard helm to steam out on a northward and eastward course toward the sound (by West Channel 01 East Channel).

On the occasion in question the course of the "Crown City" outward bound from Wooloomooloo Bay and that of the "St. Albans" inward by way of West Channel to Wooloomooloo Bay brought them at about the same time to the immediate vicinity of the head. At the moment of the collision the "Crown City" had not reached her turning point, and on the other hand the "St. Albans," coming from the West Channel had advanced southward, had the light-house abeam, and had engaged herself in the necessary helm action for making her turn.

The "Crown City" had speed of about 8 knots till just before the collision. The speed of the "St. Albans," for reasons not immediately necessary to be stated, was no more than about 4 knots. The exact course and position of the "Crown City" and the place of collision were in dispute.

The evidence at the public inquiry of witnesses from the "Crown City" and others called on behalf of the now appellants was that the " Crown City " set on her outward course off Garden Island well on the south side of the channel and continue