sink, so that what was once dry land is now far beneath the waves. This was shown by the discovery during the excavations at Ireland Island for the floating dock, of trunks of large cedar trees at considerable depths below the present sea bottom, and in dredging the channel leading into Hamilton Harbor the roof of a cave filled with stalactites was broken through, which proves that the place where it was found must have been dry land. Trunks of cedar are also found out in the reefs surrounding the islands, which are now altogether submerged.

No information, so far as I have been able to ascertain, exists as to the depth of the coral formation. A few years ago an attempt was made by an English scientific society to obtain such information by means of a diamond drill in the Island of Funafuti, in the Southern Pacific, but the experiment failed, owing to the sand filling the bore. It was then proposed to make the experiment in the Bermudas, but this as yet does not appear to have been done. It would, however, be a matter of great interest, and might prove of much value in determining the age of this recent formation, as well as settle some other questions, if such a project were carried out.

NOTE ON THE GLACIATION OF MOUNT ORFORD, P.Q. By PRINCIPAL DRESSER, St. Francis College, Richmond, P.Q. In the recent and very interesting "Report on the Surface Geology and Auriferous Deposits of South-eastern Quebec," by Mr. R. Chalmers (Annual Report Geological Survey of Canada, Volume X., New Series, Part J), it is stated that no evidences of glaciation were observed near the summit of Mount Orford. The extreme height of glacial action, from which the thickness of the greater Laurentide glacier is calculated, is thought to have been

1800 feet. Above this the mountain is said to have stood as a "minatak" or island within the glacier to a height of at least 1000 feet.

From these conclusions it is evident that the observations on which they are based did not include that domeshaped part of the summit of the mountain, which is apparently its highest point. This, which is separated from the highest of the bare and exposed peaks along the front, or southern face of the mountain, by a deep ravine, shows most undoubted evidence of glaciation. Here, near the point where a flagstaff has stood for the past few years, the rock, a fine-grained and much-altered diabase, is distinctly striated, and the whole eminence has a genererally smoothed and rounded appearance.

Fragments of clay-slate and pebbles of other rock foreign to the mountain occur here, and boulders of serpentine, evidently from the western base of the mountain, are to be seen in other places near by. The rock appears to have suffered less from atmospheric erosion than at points of about equal height a few hundred yards to the south, from which it seems reasonable to infer that it has here been protected by a thin mantle of drift, of which the transported rock fragments mentioned above are remnants, which have not been removed by summer rains or forest fires.

The direction of the glacial striæ, as measured at the flagstaff by Mr. A. H. Honeyman, of Knowlton, Que., and the writer, was found to be S. 25° E., magnetic, which fairly accords with the directions given by Mr. Chalmers for striæ caused by the greater Laurentide glacier at the foot. of the mountain. These range from S. 25° E. to S. 53° E. on the true meridian.

Reasoning from this limit of the height reached by the ice-sheet, viz., 1800 feet, Mr. Chalmers shows that if it passed over the range of hills along the United States boundary line, some 2000 feet in height, as was probably

the case, that those hills must have stood relatively lower than at present. This hypothesis is then applied to the explanation of certain high level terraces near the international boundary line, and the deformation of gravel beds around Lake Memphremagog and along the Coaticook and Salmon rivers. But in view of the evidences of ice action at a much greater altitude than 1800 feet, the hypothesis may be no longer needed. And as Mount Orford is the highest point mentioned in the area under discussion, it is, therefore, apparent that the maximum elevation reached. by the ice of this region in glacial times has not yet been ascertained, and is not likely to be from evidence obtainable in the Eastern Townships.

ON THE HEIGHT OF ORFORD MOUNTAIN.

N. N. EVANS and O. E. LEROY.

A good deal of interest is attached to the height of Orford Mountain, not only because its peak is frequently ascended by excursionists to view the magnificent panorama of lake and river, mountain and valley spread out before them when standing upon its summit, but also because certain geological theories involving a more or less accurate knowledge of the elevation are under discussion at the present time; and the various figures given for the height vary so widely as to be quite unreliable.

The recent excursion of the Natural History Society of Montreal to Orford offering a very favorable opportunity for a barometric determination of its height, the writers made careful observations upon that occasion; and as much interest in the result was expressed by many members of the Society, it was thought advisable to publish the figures thus obtained, as offering probably the most

correct of the many widely-divergent numbers given in this connection.

With respect to the determination of altitudes by means of the barometer, a few words may not be out of place, and the following, from Johnson's Theory and Practice of Surveying (Ed. 1887, p. 128), may be quoted:

"It (the aneroid barometer) has a vernier attachment, and is read with a magnifying-glass to single feet of elevation. It must not be supposed, however, that elevations can be determined with anything like this degree of accuracy by any kind of barometer. The barometer simply indicates the pressure at the given time and place, but for the same place the pressure varies greatly from various causes. All barometric changes, therefore, cannot be attributed to a change in elevation, when the barometer is carried about from place to place.

If two barometers are used simultaneously, which have been duly compared with each other, one at a fixed point of known elevation and the other carried about from point to point in the same locality, as on a reconnoissance, then the two sets of readings will give very close approximations to the differences in elevation. If the difference of elevation between distant points is desired, then long series of readings should be taken to eliminate local changes of pressure. The aneroid barometer is better adapted to surveys than the mercurial, since it may be transported and handled with greater ease and less danger. It is not so absolute a test of pressure, however, and is only used by exploring and reconnoissance parties. For fixed stations, the mercurial barometer is to be preferred.”

The observations on the trip were made with two aneroid barometers, one manufactured by Cary, of London, and the other by Usteri-Reinacher, of Zürich. The instruments were carefully compared with the standard mercurial barometer in the Observatory at McGill College, where readings were made throughout the day, and these

readings, reduced to sea-level, furnished the corrections necessary to eliminate barometric changes due to varying weather conditions. Observations of temperature were made simultaneously with the barometric observations, and these furnished further corrections in the calculation of the results.

The elevations above sea-level thus obtained were as follows:

The agreement between the results is quite as close as could be expected, but it would be of much value could a series of such observations be obtained, as the mean of a large number of results naturally carries more conviction with it than that deduced from only two. However, it may be considered certain that the height of Orford Mountain is, in round numbers, two thousand six hundred and fifty feet above the level of the sea.

It might be of interest to add that upon a clear day Montreal Mountain is visible from Orford, as was the case upon the occasion of the excursion above mentioned, and conversely, under favorable conditions, Orford is visible from Montreal Mountain, being seen above and beyond the middle of the Shefford Mountain group. This group, as viewed from Montreal, consists of a long ridge towards the observer's left, rising towards the right into two rounded bosses; Orford is seen over the ridge.

MCGILL COLLEGE, June, 1900.