APPEARANCE AND DECLINE OF MALARIOITS DISEASE. 41 



between Caledonia Bridge and the dam at that place, a space of but a 

 few yards, there were, in six weeks of 1844, nine deaths from this cause 5 

 while the rate of mortality among the population living between Caledo- 

 nia and Danville was greater than that at New Orleans, from all causes 

 combined. Of late years, however, the number of cases of disease, as 

 well as the intensity of its virus, have diminished. In the small tract 

 near Caledonia, above referred to, not a single death has occurred for 

 the last five years, while on the whole there is, according to the 

 medical gentlemen resident in the Grand River Valley, no healthier 

 part in Canada than this same locality. The prevalence of disease 

 materially retarded the settlement of the country, since who would 

 occupy land where, in spring or fall, to be ill was the rule, to be well 

 the exception ? Now, however, the cause being removed, the country 

 may be settled without danger to health, and an almost desert tract of 

 great fertility be made to add its abundant harvest to our already 

 ample annual agricultural produce. 



It would appear, at first sight, that the construction of dams on the 

 Grand River could have as little to do with the production of disease 

 as the erection of Tenterden steeple had with the formation of the 

 Goodwin Sands. But, on second thoughts, we may conceive that the 

 river water, "backing up" into, and becoming stagnant in the various 

 creeks, and being comparatively tranquil even in the main channel, 

 would allow of the deposition of putrescent and vegetable substances 

 in places where previously the running water would not have allowed 

 it to remain. Thus we can trace one possible cause of the malaria. 

 But how shall we account for the removal of the cause, while the 

 dams yet remain 1 One answer, at least, suggests itself to the enquirer. 

 The country near the source of the Grand River and its feeders, as 

 well as along its upper valley, has been rapidly cleared of its timber. 

 The snows there are now quickly melted, and the water resulting 

 therefrom, or from any great downfall of rain, is no longer retained for 

 months among the roots of the trees or in the mossy swamps. It 

 pours down at once in a sudden and violent freshet, which only 

 lasts three or four days, instead of feeding the river and maintaining 

 it at an even height for a month or two. This has a tendency to carry 

 away all floating or deposited vegetable matter into Lake Erie, instead 

 of allowing it to remain and be exposed to the sun's rays ; and thus it 

 may now counteract the effect the dams at first produced. 



It is matter for reflection, whether the geological characteristics of 



