We have more than once mentioned the Australian 'gum-tree'--_Eucalyptus_--and the remarkable properties by which it checks malaria and the noxiousness of marshes. Dr Angus Smith, F.R.S., whose valuable paper on Peat-bogs we noticed a few months since, believes that the neighbourhood of Rome, the malarious, unhealthy Campagna, might be rendered habitable by large plantations of the eucalyptus. He has visited the locality, and saw an experiment on a small scale, about four miles from Rome, which appeared to be satisfactory. 'As one enters the garden,' he says, 'there is a peculiar odour perceptible: it is fragrant, pleasant, and resinous; some compare it to that from turpentine, some to the black currant; but every one attempts to give the name of some other odour as evidently mixed with this more prominent one.... This experiment shews that men may live in health in one of the worst parts of the Campagna with proper precautions. Instead of a neglected country with scarcely a house, it might be a pleasant habitation, as it once was, for many thousands.... We are informed that the tree itself with its exhalation is quite sufficient to render a district healthy; and it is perfectly certain that if the oil is efficacious, and the evidence gives faith, those who live near must be continually taking in doses which must soon equal in amount that usually given as a cure. They must in fact be living in a constant vapour of this healing oil.' More on this interesting subject may be found in the _Proceedings_ of the Philosophical Society of Manchester, vol. 15. At the last annual meeting of the Royal Cornwall Polytechnic Society (Falmouth) there was, as usual, an interesting display of works of art and mechanical inventions, and prizes were offered which may, perhaps inspire further inventions. As examples we mention five hundred pounds for the best boring-machine applicable to Cornish mines: fifty pounds 'for the discovery of a new mineral in Cornwall or Devon likely to become commercially valuable;' and 'for a method, mechanical or chemical, of making marketable, with commercial advantage, ores or minerals produced in Cornwall or Devon, and hitherto regarded as worthless, or of little value.'