Page:Popular Science Monthly Volume 87.djvu/285

Rh  Though naked unassisted eyes Can scarce perceive them. Grains of sand Seem stones when through these glasses scanned.

The poet goes on to say that through these glasses one can read letters from such a distance that one would not believe it unless he had seen it. Then he concludes,

 But to these matters blind affiance No man need give; they're proved by science.

From the testimony of several other contemporaries we know that eye-glasses had been invented before the close of the thirteenth century.

Another important physical treatise besides Witelo's was a "Book on Weights" by Jordanus Nemorarius earlier in the century. In this work he is said to have made progress in dynamics beyond the ancients. Another invention of great use to science, clocks, was worked out during the middle ages. An innovation of great convenience in scientific reckoning and records was made when Leonardo, a merchant of Pisa, in a work written first in 1202 and then revised in 1228, brought the so-called Arabic numerals to the attention of Western Europe. Some progress in algebra was also made in the middle ages, and Roger Bacon emphasized the importance of mathematical method in scientific investigation.

It can not be shown that Roger Bacon actually anticipated any of our modern inventions, but the following passage from one of his works does indicate that an interest existed then in machinery and mechanical devices, and that men were already beginning to struggle with the problems which have recently been solved.