“I am papa’s stenographer,” she replied, “and perhaps he will dictate and I will write.  We will be glad to hear of your safe return,—­and you,—­you might ask papa.  Now, I shall soon be out of sight.”

“Please don’t,” begged Percy.  “It is still forty-five minutes ’at least,’ before the train comes.  Let me go a piece with you.  I will leave my suit case here and with nothing to carry I shall easily walk a mile in twenty minutes.  May I drive, please?”

“No, I will drive.  I want to ask you another question, and I am afraid you would drive too fast.

“You mentioned some long-continued scientific investigations which I assumed referred to the yield of crops.  What were they?”

“I meant such investigations as those at Rothamsted and also those conducted at Pennsylvania State College.  I have some of the exact data here in my note book.

“In 1848, Sir John Lawes and Sir Henry Gilbert began at Rothamsted, England, two four-year rotations.  One was turnips, barley, fallow, and wheat; and the other was turnips, barley, clover, and wheat.  Whenever the clover failed, which has been frequent, beans were substituted, in order that a legume crop should be grown every fourth year.

“The average of the last twenty years represents the average yields about fifty years from the beginning of this rotation.

“In the legume system, as an average of the last twenty years, the use of mineral plant food has increased the yield of turnips from less than one-half ton to more than twelve tons; increased the yield of barley from thirteen and seven-tenths bushels to twenty-two and two-tenths bushels; increased the yield of clover (when grown) from less than one-half ton to almost two tons; increased the yield of beans (when grown) from sixteen bushels to twenty-eight and three-tenths bushels; and increased the yield of wheat from twenty-four and three-tenths bushels to thirty-eight and four-tenths bushels per acre.

“In the legume system the minerals applied have more than doubled the value of the crops produced, have paid their cost, and made a net profit of one hundred and forty per cent. on the investment, in direct comparison with the unfertilized land.

“If we compare the average yield of turnips, barley, clover, and wheat of the last twenty years with the yield of turnips in 1848, barley in 1849, clover in 1850 and wheat in 1851 we find that on the unfertilized land in this rotation of crops in fifty years the yield of turnips has decreased from ten tons to one-half ton, and the yield of barley has decreased from forty-six to fourteen bushels, the yield of clover has decreased from two and eight-tenths tons per acre to less than one-half ton, while the yield of wheat has decreased only from thirty bushels to twenty-four bushels.  As a general average the late yields are only one-third as large as they were fifty years before on the same land.  Wheat grown once in four years has been the only crop worth