PLASTER OF PARIS IN AGRICULTURE 61 



ammonia, that is to say prevents its being dissi- 

 pated. 



"To illustrate the fertilizing effect of plaster of 

 Paris on lucerne, the following incident is related. 

 Franklin, one of the chief glories of the United States 

 of North America, aware of the great fertilizing 

 power of plaster, wished to extend the agricultural 

 use of this substance among his fellow-citizens; but 

 they, clinging to old customs, would not listen to 

 him. To convince them, Franklin spread plaster 

 over a field of lucerne by the side of the most fre- 

 quented road leading out of Philadelphia, but spread 

 it in such a way as to form letters and words. The 

 lucerne grew all over the field, but much taller, 

 greener, and thicker where the plaster had been ap- 

 plied, so that the passers-by read in the field of lu- 

 cerne these words traced in gigantic letters : ' Plas- 

 ter of Paris was applied here. ' The ingenious expe- 

 dient was a great success and plaster was very soon 

 adopted in agriculture." 



"The doubters must have been convinced," said 

 Jules, ' ' on seeing those big green letters rising above 

 the rest of the lucerne. Did not Franklin do some 

 other remarkable things? I remember the name; I 

 have seen it several times in books." 



"Yes," replied his uncle, "Franklin became by his 

 learning, one of the most remarkable men of his time. 

 Among other things, we owe to him the invention 

 of the lightning-conductor, that tall pointed iron rod 

 erected on the roofs of buildings to protect them 

 from the thunderbolt. It was he who first had the 



