CONTRASTS. 117 



LECTURE VI. 



EXPLANATORY CHARACTER, OF OUR THEORY CONTRAST 

 OF THE HEALTH OF SEASONS AND PLACES. SUDDEN 

 ONSETS IN AFRICA. THE MAREMMA VOLCANIC ERUP- 

 TIONS. SPUR TO VEGETATION. REVOLUTIONS IN LOCAL 

 HEALTH. FAIRY RINGS. NON-RECURRENCE OF SOME 

 DISEASES. LIEBIG'S THEORY. EPIDEMIC MOST FATAL 

 AT ITS ONSET. DRY SANDY PLAINS SICKLY. RECAPITU- 

 LATION. 



INDEPENDENTLY of any observable cause, the crops of 

 various kinds differ in a remarkable manner in different 

 seasons. Most of you must have seen the wonderful pro- 

 duction of the fruits of all kinds in certain autumns. A 

 year or two since, the trees actually bent down and broke 

 under the immense load of apples, which were left to rot 

 in the fields in many places, for want of the means of se- 

 curing them. No cause for this exuberance was observ- 

 able. Farmers sometimes have good crops even in oppo- 

 sition to the inclemency of the season, and as often, under 

 the most auspicious meteorology, are chagrined at the un- 

 accountable shriveling, or paucity of their grain. So is it 

 with the fungi, which, in opposition to hostile meteoration, 

 spring up in unusual places, or abound prodigiously in cus- 

 tomary positions. Thus in 1798, a year of protracted heat 

 and drought, Condie and Folwell reported, as remarkable, 

 the abundant production of various classes of mushrooms. 



