LIGHTNING CONDUCTORS. 215 



"with real advantage each rod protecting an area of one 

 hundred yards. Thus it is that science ministers to our 

 service ; and how much more pleasing is it to contem- 

 plate the lightning, with the philosopher, as an agent 

 destroying the elements of pestilence, and restoring the 

 healthfulness of the air we breathe, than with the 

 romancer, to see in it only the dreaded aspect of a 

 demon of destruction. 



The laws which regulate the spread of a pestilence 

 are unknown. The difficulties of the investigation are 

 great, but they are by no means insurmountable. A 

 plague passes from the east to the west across the world 

 it spreads mourning over the gayest cities, and sorrow 

 sitteth in the streets. The black death rises in the 

 Orient : it goes 011 in unchecked strength, and only 

 finishes its course when it has made the circuit of the 

 civilized world. The cholera spreads its ebon wings 

 mankind trembles watches its progress, and looks 

 upon the path which is marked by the myriads of the 

 dead, who have fallen before the dire fiend. The 

 diseases pass away the dead are buried, and all is 

 forgotten. The rush and the riot of life are pursued : 

 and until man is threatened with another advent, he 

 cares not to trouble himself. Accompanying the last 

 visitation, there appear certain peculiar meteorological 

 conditions, which point a line of inquiry. It may or 

 may not be the path which leads to the truth, but 

 certainly its indications are worthy of careful ex- 

 amination. It may be asked, can weak man stop a 

 pestilence ; can a mortal' s puny hand retard the afflic- 

 tions of the Almighty? The question asked it must 

 be answered in reverence, yet without fear. No 

 human power can produce a change in the physical con- 

 ditions of the earth, or of the air ; and if our diseases 

 are connected with those changes, as beyond all doubt 

 .a number of them are, they lie above man's controL 

 But when there are indications that causes secondary to 



