318 AMERICAN AGRICULTURE. 



received their annual stores of newly cut hay and grain. 

 The humid gases, generated by the heating and sweating 

 of the hay, which immediately follows its accumulation in 

 closely-packed masses, offers a strong attraction to electri- 

 city, just at the time when it is most abundant. It is an 

 object of peculiar importance to the farmer, to guard his 

 buildings, at such times, with properly constructed lightning 

 rods ; and they are a cheap mode of insurance against fire 

 from this cause, as the expense is trifling and the security 

 great. 



It is a principle of general application, that a rod will 

 protect an object at twice the distance of its height above 

 any given point, in a line perpendicular to its upper termin- 

 ation. Thus a rod attached to one side of a chimney of 

 four feet diameter, must have its upper point two feet above 

 the chimney to protect it. Its height above the ridge of a 

 building, must be at least one half the greatest horizontal 

 distance of the ridge from the perpendicular rod. 



Materials and manner of construction. The rod may 

 be constructed of soft, round or square iron (the latter being 

 preferable), in pieces of convenient length, and not less than 

 3-4ths of an inch in diameter. These should not be hooked 

 into each other, but attached either by screwing the ends 

 together, or forming a point and socket to be fastened by a 

 rivet, 'so that the rod when complete, will appear as one 

 continuous surface of equal size throughout. If a square 

 rod be used, it will attract the electricity through its entire 

 length, if the corners be notched with a single downward 

 stroke of a sharp cold chisel, at intervals of two or three 

 inches. Each of these will thus become a point to attract 

 and conduct the electricity to the earth. A bundle of wires, 

 thick ribbons, or tubes of metal, are more efficient con- 

 ductors, than an equal quantity of matter in the solid round 

 or square rods, as the conducting power of bodies, is in the 

 ratio of their surfaces. No part of the rod must be 

 painted, as its efficiency is thereby greatly impaired. The 

 upper extremity may consist of one finely-drawn point, 

 which should be of copper or silver, or well-gilded iron, to 

 prevent rusting. The lower part of the rod, at the surface 

 of the ground, should terminate in two or three flattened, 

 divergent branches, leading several feet outwardly from the 

 building, and buried at the depth of perpetual moisture, in a 

 bed of charcoal. Both the charcoal and moisture are good 

 conductors, and will ensure the passage of the electricity 



