PLASTER OF PARIS IN AGRICULTURE

“In agriculture plaster of Paris has by no means the importance of lime; nevertheless it produces excellent results on clover, sainfoin, and lucerne. It is used in the spring for sprinkling the young leaves when they are still damp with the morning dew. Still, foggy weather is the most favorable for this work. Plaster also acts well on rape, flax, buckwheat, and tobacco, but has no effect on cereals.

“The intelligent farmer puts plaster of Paris to still another use. In every dunghill there is always going on a slow combustion, or fermentation, giving forth ammonia in vaporous form; and this ammonia escapes into the air as a total loss, whereas it ought to be retained as far as possible in the manure, since the compounds of ammonia constitute the source whence plants obtain nitrogen. Therefore to prevent this waste, plaster is sprinkled over the dunghill. Sometimes, too, it is sprinkled over each layer of manure as the pile rises. The plaster absorbs the ammoniac vapors, gives them a little of its sulphuric acid, and converts them into a compound, sulphate of ammonia, which is proof against vaporization. Hence we say that plaster of Paris fixes [61]ammonia, that is to say prevents its being dissipated.

“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 frequented 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 applied, so that the passers-by read in the field of lucerne these words traced in gigantic letters: ‘Plaster of Paris was applied here.’ The ingenious expedient 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 [62]superb audacity to evoke the lightning from the midst of the thunder-clouds, to direct it according to his wishes, and to bring it to his feet that he might study its nature. One stormy day in 1752 he went out into the country near Philadelphia in company with his young son who carried a kite made out of a silk handkerchief tied at the four corners to glass rods. A pointed piece of metal terminated the apparatus. A long hemp cord, with a shorter cord of silk tied to the lower end, was fastened to the kite, which was then sent up toward a black thundercloud. At first nothing happened to confirm the previsions of the American sage, and he was beginning to despair of success when there came a shower of rain and with it a flash of lightning. The wet cord proved a better conductor than when dry. Without thinking of the danger he ran, and transported with joy at having brought within his reach that which causes thunder, Franklin put his finger near the cord and made little spurts of fire dart out, lighted brandy from these sparks out of the sky, and only brought his perilous experiment to an end when he had fully determined the origin and nature of thunder and lightning. This was the way he studied the mystery at close quarters, discovered its nature, and finally succeeded in protecting buildings by means of a pointed iron rod.

“Benjamin Franklin was born in Boston, North America, in 1706. He was the youngest1 of seventeen children. Hence, as his father was a poor tallow-chandler and soap-boiler, he could not acquire at home anything beyond a knowledge of reading, writing, and arithmetic. At ten years of age he was taken from school and set to performing small tasks about the house. He cut candle-wicks and poured the tallow into the molds, waited on customers in his father’s shop, and ran errands. His work brought him in a few pence which he did not yet know how to spend judiciously. He tells us the following little story on this subject, which we may all profit by.

“ ‘One day,’ says he, ‘finding myself the possessor of a handful of coppers, I ran out to buy some toys, when a little boy of about my own age happened to pass that way with a whistle in his hand. Delighted with the sound of the whistle, I proposed to my comrade to exchange all my money for his musical instrument. To this he very willingly agreed. Elated with my purchase, which I thought very fine, I returned home, where I continued whistling to my great joy, but to the great displeasure of the ears of my family. I told them of the magnificent exchange I had just made. My brothers and sisters made fun of me, saying that for the price I had paid I might have bought dozens of such whistles at the toy-shop. Only then did it occur to me what fine things I might have bought with my money, and I began to cry with vexation. Chagrin at the exchange I had made now caused me more pain than the whistle had before given me pleasure. This little incident made an impression [64]on me that has never been effaced and has been of service to me on more than one occasion. Ever since, whenever I am tempted to buy some useless thing, I say to myself, “Do not pay too much for your whistle”; and so I save my money.’ ”