CALCAREOUS MANURES-APPENDIX. 295 



one place, should be very irregular, and the difference be often totally inex- 

 plicable from any known causes, or variation of circumstances. 



According to the views presented, there must be more or less malaria 

 (or the gaseous products which, under certain conditions, form malaria,) 

 evolved in every country where there is much vegetable matter to ferment, 

 and sufficient warmth of climate to carry on fermentation. But, in the 

 small quantity which is unavoidably extricated in every such temperate 

 and fertile country, these products seem to be harmless. Perhaps a small 

 quantity is absorbed as food by growing plants, and this aids the produc- 

 tion of the earth. If so, this beneiicial operation is made easy by another 

 quality of malaria, which is well established as true. This is, that though 

 it is so expanded by the sun as to rise above the lower air, still it remains 

 on the surface of the earth in the night, after being extricated, or perhaps 

 descends again from above, when condensed by the cold night air, and of 

 course lies in contact, through the night, with growing plants. Hence it is, 

 that sleeping on the ground, or in the lowest apartments, and being exposed 

 to the night-air, invites the attacks and increases the virulence of malaria; 

 and hence also it is, that the keeping of fires at night, even in warm 

 weather, has been found highly useful to health, in places much subject to 

 autumnal fevers. 



Though it may then be theoretically true that every good soil, in warm or 

 temperate climates, is throwing out malaria to a certain extent, it is only 

 large quantities that are hurtlul; and in practice, we have only, if possible, 

 to avoid the formation of the hurtful excess of the products of fermentation. 

 If, in lower Virginia, we can guard against the existing and increasing 

 excess of malaria, our situation would be one of the healthiest in the world. 

 For while we are comparatively free from the many and fatal disorders of 

 the lungs to which the inhabitants of northern, and what are usually and 

 improperly called healthy countries are peculiarly subject, we have no 

 source of disease peculiar to our location, save this one, which, I lully be- 

 lieve, it is within our power to guard against. 



Putrefying animal matter alone, however offensive in scent, is supposed 

 not to produce malaria. It cannot be doubted but that decomposing vege- 

 table matter is its source, because there is no production of it where there 

 is no such material. Still, vegetable matter alone, or even when mixed 

 with some putrescent animal matter, does not seem generally to produce 

 malaria in great quantity, or with manifestly injurious effects on health. 

 Thus, the gradual fermentation and rotting of the litter in cattle-yards, 

 when left to stand through summer and autumn, or when the same was 

 heaped and so left, (as was formerly the general practice in lower Virginia 

 on all farms where manure was an object of care,) never was known to be 

 certainly and highly injurious to the residents on the farm. Doubtless, 

 malaria, and to an injurious extent, was always thus produced ; but I have 

 never known a sensible difference in regard to health, between years when 

 either of the practices above-named were pursued, and when the material was 

 carried out and applied to the fields in the spring, before fermenting. Yet, 

 if judged by the test of some of the causes and effects as described and 

 reasoned from by writers on malaria, one well-filled yard of litter, rotting 

 through summer, ought to have produced enough malaria to kill half the 

 inhabitants of the farm ; and effects, in general, which would have been so 

 disastrous, and so sure, as to leave no doubt of the cause of the evils, and 

 of the absolute necessity of preventing their future recurrence. 



But the putrefaction of vegetable matter, mixed with other things, as 

 earth and water, and under peculiar circumstances, (though neither the 

 precise admixture nor the circumstances are known,) produces disease to 



