PRODUCED BY MAN. 797 



quarters of the world we have more or less well-established histories 

 of belts or curtains of trees protecting towns from malarious and 

 anti-sanitary influences. 



Secondly, though doubt may be raised (e.g. by M. J. Bellucci, cit. 

 'Athenaeum/ March 14, 1874, p. 360) as to the giving off by trees 

 of ozone into the air, there can be no doubt as to anotlier mechanical 

 effect besides the one already dwelt upon in the way of breaking 

 the force and the fall of raindrops, and thereby preventing, 'pro tanto,, 

 the over-rapid flowing away of such rain and the over- violent wash- 

 ing away of the soil. Simple as this action is, it is, when coupled 

 with the action of the roots and their spongioles, to which it gives 

 a fairer chance of coming into play, one of the most important 

 which a tree in leaf exercises. Finely divided rain sinks into the 



West Indies, and from Guiana. Lord Mark KeiT (see ' Report on Measures adopted 

 for Sanitary Improvements in India for June 1871 to June 1872,' p, 14) did much 

 planting in Delhi in 1864, and, on coming eight years later to take stock of the 

 eifects of his hygienic work, was able to persuade himself that the almost entire dis- 

 appearance of the Delhi boil was due to this particular cause. But the Indian 

 Government had to report in the succeeding year's volume of the same series, p. 17, 

 that they had not received from the authorities they had consulted ' reliable data to 

 warrant any general conclusions being drawn as to the effect of trees and vegetation 

 on these sores.' Still they proposed ' to institute a more particular inquiry into the 

 matter, and to submit a Report on the investigations in due course.' Upon this 

 subject something may be found in Mr. Menzies' 'Forest Trees and Woodland 

 Scenery,' 1875, p. loi, q. v. ihique ah ipso auctore necnon a me citata. Since the 

 appearance of Mr. Menzies' work the literature relating to the Eucalyptus globulus as 

 an agency for 'purging the unwholesome air' has attained a great development. 

 Especially to be recommended is a paper, ' The Eucalyptus near Rome,' by Dr. R. 

 Angus Smith, F.R.S., published in the ' Proceedings ' of the Literary and Philosophical 

 Society of Manchester, vol. xv., No. 9, pp. 150-164, 1876, as also some papers in the 

 •Edinburgh Medical Journal,' February 1878, and May 1879, pp. 1052-1053, by Dr. 

 Bell. And what is better even than good memoirs, good progress has been made in 

 the way of actually planting this tree by no less conspicuous warriors than Garibaldi 

 in the Roman marshes, and by Sir Garnet Wolseley in Cyprus. I have not, however, 

 heard of any further development of the use of the Helianthus annuus as an anti- 

 malarious agent, nor of the adoption of Mr. Menzies' recommendations of the employ- 

 ment of the horse-chestnut, the sycamore, or the balsam poplar and white jDoplar for 

 the same purpose. To the references given 1. c. may be added, as speaking in the 

 same sense, Becquerel, 'M^m. Institut/ xxxv., 1866, p. 444, and Boudin, 'Gdographie 

 et Statistlque Medicales,' vol. i. p. 229. Much has been written by the two last- 

 named writers on the electrical action of trees ; I will quote the following sentences 

 from the latter of the two, I.e. : 'Eufin le ddboisement doit ^tre considdrd comme 

 Equivalent k la destruction d'un nombre de paratonnerres Egal au nombre d'arbres 

 qu'on abat ; c'est la modification de I'dtat dlectrique de tout un pays ; c est Taccumu- 

 lation d'un des Elements indispensables k la formation de la grgle dans une locality oh 

 d'abordcet Element se dissipait inEvitablement par I'action silencieuse et incessante 

 des arbres. Les observations viennent k I'appui de ces deductions thEoriques.' 



