“In Upper Canada these diseases prevail most among the troops stationed along the course of the great lakes from Kingston to Amherstberg, they are almost unknown at Penetanguishene and By Town. The settlers who reside even at the distance of a few miles inland rarely suffer from them; yet the districts enjoying this exemption are in many parts covered with lakes, intersected by streams, and abound in marshy ground, decayed vegetation, and all the other agencies to which the origin of this type of fever is generally attributed. A reference to the report on Nova Scotia and New Brunswick will also show that though the same agencies exist to a similar extent at some of the stations in that command, intermittent fevers are almost unknown. “These diseases, too, are said to be comparatively rare wherever the surface is covered with dense forests, even though the ground is wet and marshy. The vicinity of lands recently cleared is most subject to them, particularly meadows or open patches of the forest, which, though denuded of trees, have not been brought under cultivation. It would appear, too, that their prevalence is diminishing with the progress of agricultural improvement; for it will be observed, on reference to the Abstract of Diseases, No. III. of Appendix, that since 1831--a period during which this province has been rapidly advancing in wealth and population, and many important changes have taken place in the vicinity and stations occupied by the troops--intermittents have become comparatively rare, the proportion attacked having been scarcely one-tenth part so high as the average previous to that period. Intermittents most frequently occur from July to September, when a high temperature prevails; but they are also to be met with, though more rarely, in spring, when that agency could only operate in a trifling degree to induce them. Though a source of inefficiency among the troops, they add but little to the mortality, as not one case in a thousand proves fatal. A person who has been once attacked is exceedingly apt to suffer from them again; but this susceptibility is easily removed by change of residence to the northern parts of the province, or to Lower Canada. “In some years, fever also manifests itself along the borders of the lakes in the remittent form, but not of so fatal a character as in the West Indies or the Mediterranean; for only one case in sixteen is found to have proved fatal among the troops.