12 Introduction. 



of the rays of the sun, or their vertical direction, is of 

 the greatest importance in relation to vital manifesta- 

 tion. 



Barometric pressure and humidity are equally important in 

 relation to health and disease, but vital manifestation is in 

 direct ratio to the vertical rays of the sun and the amount 

 of moisture and barometric pressure. Hence, from a vito- 

 physical point of view, these rank the highest in regard to 

 the products of the earth, but not in regard to the health of 

 man. 



Though the spots on the sun have a certain relation to 

 magnetic conditions on the earth's surface, as yet no im- 

 pression upon vital phenomena has been traced as recurring 

 with their appearance, or ceasing with their disappearance ; 

 therefore, as apparent agents in relation to vital manifesta- 

 tion, they may be accounted as nil. 



Volcanoes and earthquakes, though frequent and violent, 

 at times when epidemics have broken out, yet the occur- 

 rence of these terrible commotions within, which terminate 

 in convulsions and changes on the surface of the earth, 

 by no means runs parallel with epidemics. Whilst they 

 are not viewed as causes of epidemic disease, but chiefly 

 as coincidental, yet it is more than probable that they 

 have an endemic influence attached to them, as imme- 

 diately before and after their accession, dry, close, and 

 sultry weather is observed for days, or much local elec- 

 tricity, and possibly emanations in the form of gases, &c., 



