"The principal geological formations supporting the flora described may be summarised under the names of blue granite, acid granite (denoting an abundance of silica), and indurated claystone formation. The blue granite occurs chiefly between Deepwater and Stannum, also between Deepwater and Tent Hill. The acid granite produces the flora between Stannum and Torrington, while the indurated claystone is found around Emmaville. The flora of the acid granite area is profuse compared with that of the more open blue granite country, though the latter produces a much better soil. These igneous rocks have been very fully described by Messrs. E. C. Andrews, B.A., and J. C. H. Mingaye, F.I.C., F.C.S.* Some figures representing constituents of these rocks in other localities, taken from the paper by Messrs. Andrews and Mingaye, are most instructive.

"It will be seen that the acid granite has a much higher percentage of silica, but the blue granite possesses a greater proportion of those ingredients which produce good soil."

"It has been noticed that many plants which belong to the Western Slopes and which are restricted to comparatively low levels in the south, appear to ascend very considerably on western New England. This great difference is probably to some extent due to the very cold influence in the south, which radiates from the snow-clad heights of Kosciusko, whose altitude exceeds 7,000 feet. If a similar mountain area of equal height existed in the north of this State, it would be likely to prevent the ascent of many western species to their present elevations. If, on the other hand, the local conditions were the same throughout the Mountain Area, the upper limit of the plants of the Western Slope would rise with greater regularity along a more even grade. It is probable the diminished effect in the north of the cool southerly wind exercises some important influence in the matter, as although the elevation is greatest in the south, the land mass, which exceeds, say, 3,000 feet, is greater in extent in the north."

Although Sterculia diversifolia (Currajong) was found growing close to Stannum, it was on an andesite formation, and was not noticed on the granite This species is also rare on the purely sandstone soils around Sydney and on the Blue Mountains. The fact of its occurrence at an elevation of about 3,400 feet in this Mountain Area, while at the same time it flourishes in the dry Interior near Cobar, etc., furnishes evidence of its adaptability to environment. Its home, however, is usually below

an altitude of 2,000 feet in New South Wales."

"Eucalyptus albens is the White or Grey Box tree which practically defines the east and west limits of the area referred to by me as the

* Records Geological Survey N.S. W., 1907, Vol. VIII.

Western Slopes; and although south of the Murrumbidgee it is rarely found at an elevation exceeding 1,300 feet above sea-level, it climbs to 3,000 feet around Emmaville, the highest point observed being on the Bald Nob, which reaches about 3,200 feet. It is of interest to find that this tree manages to ascend almost to the New England Plateau, but this it accomplishes by creeping up the sides of the valleys where it secures shelter from coastal influence, for its great desideratum is a western aspect. North of Emmaville it follows up the valley of the Beardy River and Glen Creek, gradually establishing itself at such high levels as to come within some of the winter snow-storms. It advances towards Glen Innes along the valley of the MacIntyre River above Inverell, where the basaltic formation suits it so admirably, and is the principal tree in giving a characteristic appearance to the lccal flora,

"Reflecting on the qualities which a plant possesses for resisting extremes of temperature and moisture, the thought is suggested that possibly in some instances after thousands of years of gradual adaptation to opposite conditions, extreme forms are evolved which in time may be regarded as separate species. Something of this kind may explain the great similarity which exists between Eucalyptus albens of the west and Eucalyptus hemiphloia F.v.M, a common Box tree along the coast. It is still a matter of opinion among botanists whether these are two distinct species, or one a variety of the other; but it seems highly probable, considering the close affinities between them, that both had a common origin, and have developed their present characteristics owing to the various influences of environment."

The 5-Chain Standard in Ceylon.

HE following extract from the Annual Report of the Lands Department of Ceylon, for 1907, in which the laying-down of a five-chain standard is described and illustrated, will be of interest to members, as showing what is being done in other countries in the matter of convenience for surveyors.

A similar standard for the use of the surveyors of New South Wales has long been required, and it is a matter of regret that it has not been supplied.

The standard at the Lands Department here is neither accurate nor convenient; the 100 ft. length is 03 inch too long, and the 66 ft length is 04 inch too long, differences which are far too high, and, for our credit's sake, should be eliminated. The standards are laid down in a dark, draughty corridor in the basement of the Lands Department, where it is impossible to tell the temperature of the chain at the time of comparison, and where candles are necessary to see the terminal marks on a bright day.

We are glad to learn from an authoritative source that it is probable that a new standard will be laid down in the near future. A high degree of accuracy will be obtained by the use of Invar, while convenience of access will be studied.

Early in 1906 six large concrete cubes, 4 feet side, were laid down, into which stones 1 foot square and 18 inches deep were inserted, one chain apart. Light brick walls were built between the concrete blocks to support the tapes under test, the walls being separated from the blocks by gaps two inches wide, to avoid any possible displacements through expansion or settlement, the whole forming a practically continuous surface five chains long. All the necessary precautions were taken to allow the rain-water to drain off rapidly from the surfaces of the copings, etc., and the whole was allowed to settle thoroughly during

two monsoons.

The first question considered was that of the marks to be adopted. It was essential that those used should be available for testing measures both coarsely, for ordinary purposes, and with precision whenever required; that they should withstand great wear and tear, and offer the greatest permanence possible; and that they should be set so accurately as not to require any correction in ordinary testing. In order to fulfil these conditions it was necessary that the marks should be at the same time fine enough to allow of accurate setting under a high-power microscope, wide enough to be easily seen with the naked eye, and deep enough not to wear away in a short number of years.

After a number of experiments carried out in the latter part of 1906, the following method of making the marks was finally adopted :Cubes of light bronze, 1 inch on a side, were carefully cut in halves, and provided with pins to keep them in position Each of the internal faces

of the half-cubes was carefully and smoothly tinned, and sheets of pure copper inch thick were soldered to them. The outer faces of the copper were also tinned, both halves put together, and heated until the tin began to flow freely. The cube was then lightly clamped in a vyce, and after allowing the tin to set slightly for six to seven seconds, great pressure was brought to bear upon it, and the whole was allowed to cool in position. It was then taken out, filed, ground, and polished. The resulting marks are all that can be desired; they can only wear out with the cubes; to the naked eye the mark shows as a dark brown band' inch wide upon a yellow ground, while under a power of 50 diameters the aspect is as shown in Fig. 1 opposite, a, a' being the edges of the copper sheets, b an extremely fine, dark line produced by tin junction between them, c, e similar lines between the copper and the bronze.

A

The cube at the starting stone was carefully soldered to a flat brass disc, 3 inches in diameter and inch thick, and securely cemented into the centre stone flush with its surface. The other cubes were mounted upon a square brass bar screwed at both ends, and sliding into the bearings of the small casting as shown in Fig. 2, where c is the cube, b the bar, n, n' nuts screwed on the outside of the bars to allow of the cube travelling along the axis of the bar for about an inch on each side of the centre line, and of its being securely clamped in any position; and ta tag for securing the casting in position.

The stones were next cut into, and the cubes being placed at the centre of the casting, and the bar b well greased, the castings were cemented to the

stones by their tags, the cement being allowed to rise about 4 inch above the base, care being taken that the axes of the bars were accurately in line, and the faces of the cubes flush with the surfaces of the stones.

*

The standards of lengths available were an Invar tape, 200 feet long, subdivided by three cuts a chain apart, and a brass rule 36 inches long, by Troughton and Simms, said to have been tested by them in 1892, and stated to have then been correct at 80° F. No details are available as to where and how or to what degree of accuracy the test was conducted. The Invar tape was tested at Kew in December, 1905, and is stated to to have been 0.31 inch short on the flat at 16·67° C. under a pull of 10 kilograms. This tape was received in April, 1906, and was carefully preserved until it was used on the standard., Two comparator microscopes by the Cambridge Scientific Instrument Co. reading to 1 millimeter were also available.

The first operation was to test the inch divisions of the brass yard, in order to find the value of the micrometer divisions of the comparator microscopes. In order to shorten the work, divisions 24 inches apart were taken The yard was mounted upon rollers secured in light frames supplied with levelling screws, and one end of the yard abutted against a sliding piece commanded by a well-cut screw, by means of which the whole yard could be shifted longitudinally by small amounts. The two microscopes

were mounted 24 inches apart to read the divisions on the edges of the bar. By this means it was found that the length between the divisions O and 24, 1 and 25, 2 and 26, 3 and 27, 4 and 28 were equal with no perceptible error, while the others, 5 to 29, etc., along the bar showed irregularities. The distance between the microscopes was then shortened to 4 inches, and the divisions between 0 and 28 were carefully tested, and the resulting readings showed that this yard was remarkably well divided for the first 28 inches. Careful comparison of results led to the portion between 1 and 25 being selected for future work, and the divisions 1 to 11 as being the best for determining the value of the runs of the microscope screws.

The tape was next stretched under a pull of 10 kilograms (22 lbs.), and the distance between the 200 ft, mark and the three-chain mark, which should have been exactly 2 feet, was compared with the yard between 1 and 25 in. Assuming that the errors of the three cuts were proportional to the error of the 200 feet cut, and due allowance being made for the temperature of both tape and bar, the distance between divisions 1 to 25 was found to be short of the assumed distance between the cuts by 0-0011 inch; and as the divisions of the yard had been previously found to be sensibly constant, the value of the runs of the screws could bə determined with some confidence. This was now done for each of them, between the divisions 1 to 11 on the yard, the result being that, for microscope No. 1, 1 inch = 25-430 divisions, and for microscope No. 2, 1 inch = 25-456 divisions. The 24 inches of the yard were noxt compared with two older yards supposed to be also correct at approximately the same temperature, and they agreed so closely that it was decided to adopt the length between 1 and 25 inches as being the correct length of two feet.

The average temperature of the air at Colombo deduced from the hourly values for the last ten years, between 6 a.m. and 6 p.m., was found to be 83° F., which was taken as the standard temperature. With

As these cuts are not quite parallel, the edge used in measuring is the one facing the observer when the zero cut is to his right and the 200 ft. cut to his left.