The continual applications received by us, during the last few years, for further data concerning the physical and chemical properties and commercial possibilities of the oil products of the Eucalypts-than those given in the first edition, which has now been out of print for some time-were the chief incentives which moved us to place our latest researches on these wonderful trees into the present book form.

In the previous edition the species more particularly investigated were those restricted to the South Eastern area of the Continent, but since that publication was issued the research has extended to species found in all the States of the mainland, as well as those of Tasmania.

No pains have been spared in the endeavour to insure that the material worked upon was true to name - botanically correct ; and in order to determine the constancy of the product from individual species, material has been collected from widely separated localities, so that commercial requirements for uniformity might be satisfied.

The collection of such a mass of material for investigation was no small task, the genus being distributed over an area of about 1,000,000 square miles of territory, more particularly when it is understood that, with two or three exceptions, all the distillations were carried out in Sydney under our own supervision, the necessary botanical control being, in this way, well assured.

Eucalyptus species are often very local in their distribution, frequently growing in localities difficult of access and far from rail and road communication, and although expert collectors were employed for this work, yet the difficulties of location were none the less in evidence.

As illustrating this difficulty of collection in such sparsely settled countries as Australia and Tasmania, Plate cxx is given.

In the main the scheme of the original edition is again followed, although, of course, much amplified in various directions, in agreement with the many new discoveries and fresh facts brought to light during the last twenty years.

Where possible the data given in the first edition have been verified and extended by further researches on new and larger quantities of material of the same species, growing under varying climatic and geological conditions. With one or two minor exceptions the chemical and botanical information as previously recorded still stands, and is supported by these more extended investigations.

To every section has been added the accumulated results of our labours in this direction, during past years, in the research laboratories of this Institution.

These results clearly show that in the Genus Eucalyptus, Australia has a commercial Forest asset of so diversified and valuable a nature that it has no compeer in any other genus in the whole botanical world.

Especially is this noticeable in the great variety of timbers and oils, the latter of which is specially treated in this work, the former being monographed in a separate publication by one of us, and issued from this Mus.um:--No. 23 of the Technical Education Series.

Since the publication of the 1st edition, the Eucalyptus oil industry has expanded considerably its scope of usefulness in the industrial world, as for instance the utilisation of certain oils in the mineral flotation process for the extraction of metallic sulphides, for perfumery purposes, for solvents, and the preparation of proprietary articles.

Besides the amplification of the letterpress and subject matter in the first edition, many new features will be noticed, as, for instance, the sections of leaves in colour photography, magnified by various diameters, which will give some idea of the position of the oil in the leaf. Chromatic photography was employed in this way in order to show more clearly the differentiation of the anatomical structure of the leaf. The bark illustrations also give some idea of the natural groups into which the trees are divided on a cortical system.

A series of plates is added, showing the various systems or methods of extracting the oil from the leaf in Australia.

As we have now reached the age limit for retirement as laid down by the Government Service Regulations, and so will shortly leave this field of our scientific activities in which we have laboured so long, and, we hope, with some small measure of success, this will be the last joint monograph by us. We therefore take this opportunity of placing on record our appreciation of the far-sighted policy of our Department of Education (of which this Museum is an integral part)-a policy that has encouraged and enabled us in our research work, to endeavour to bring to light for the benefit of pure and applied science some of the hidden mysteries of Australia's unique and wonderful Flora.

November, 1920.

R.T.B. H.G.S.