Whenever and wheresoever he congregates into masses, there “the earth, the air, and the waters,” receive modifications from him, which, when injurious, he alone can rectify. The most consolatory view which man can take of such a condition of things is unquestionably to believe them to a great extent remediable by his own labour and intelligence; for even should he fail, there remains to him the consolation that he has done his best. CONCLUDING CHAPTER. AUTHOR’S THEORY OF MALARIA. It is easier to pull down than to build up; easier to refute than to convince; easier to find fault than to suggest a remedy: and this reflection may occur, and no doubt has occurred, to those, be they few or many, who have perused the preceding chapters of this work. It may now be asked of me explicitly, What is your theory? What is your remedy for the evils complained of? To this I might reply, as the immortal historian of the “Decline and Fall” is said to have done, “If you have read certain chapters of my work with sufficient attention, you may extract from them my meaning and my views;” but as this might imply on my part either a Teutonic love for obscurity in phraseology, or a fear to commit myself to any theory, I shall here sum up in a few words the views I have arrived at after much reflection on the matter, during a long and active life passed in a country supposed to be a hotbed of malaria, the great source indeed of malaria in Western Europe, that land for which nature has done so little and man so much.