For out-door culture Australia offers but little to the Eastern United States; but some eucalyptus and acacia may be utilized for South California, Arizona and Southern Texas; but E. amygdalina, E. parviflora and E. Gunnii, (all tall timber trees), may endure winters of yours in more northern States, as they adorned the Australian Alps. The Italians under the leadership of Count Torelli, I have recommended to plant Eucalyptus on the malarian, forbidden swamps near Rome, after E. globulus (but only in its young sappy state), was largely destroyed bythe unusually severe winter cold of the year before last. But this time the experiment is made with E. amygdalina, the richest oil-yielder of all eucalyptus, and one which will live in a cold climate where no E. globulus will stand through the winter months. For timber, however, the E. amygdalina is far inferior to E. globulus and many other sorts. E Gunnii and E. parviflora yield good timber, but their hygienic value is not equal to that of E. amygdalina, and the growth of none of them is as fast as that of E globulus; still they are all trees of comparative celerity of growth, especially in somewhat humid soil.

I still believe, that much might be done to subdue the yellow fever of New Orleans and other southern places in the States, if all back-yards were planted with eucalyptus; but should the climatic condition not admit of it, I would earnestly impress on all concerned to plant your most terebinthine pines at New Orleans, and by the millions. Their volatile oil acts much like that of the eucalyptus, as from its emanations originate dioxyde of hydrogen and ozone, the most powerful oxydisers and therefore destroyers of microorganism and the gases in which they dwell. I have given officially the same advice to Holland for trying to suppress the miasmatic exhalations which cause the marsh-fever there; and I have sent the eucolyptography to the National Board of Health of North America, so that my views on the hygienic value of the eucalyptus (and pines) have become known to the Board. Perhaps you are inclined to take up this important question in your highly valuable and widely circulating Monthly.

I am engaged on determining at present the percentage of volatile oil in the twigs (leaves and young bark and young wood) of various pines, as this has an important bearing on the sanitary value of each species of fir.

[The above from Baron Mueller is from private correspondence but of so much public interest that we hope he will pardon its publication. - Ed. G. M.1