the contact point was 398 paces, and thus it was nearly one-seventh of the mean distance. After this contact, the ball first bounced 215 paces; second, 275; third, 279; fourth, 150; fifth, 81; sixth, 73; seventh, 78; and finally eighth, 124. Thus the horizontal throworiginal: "iactus horizontalis." This refers to the total distance a projectile travels along the ground., including those eight bounces, was 1750 paces. This was nearly half of the mean distance. Studious readers may put the finishing touch to these matters with various experiments of their own.

Fourth, I have now been informed about the number 576 grains, which make up a Roman ounceoriginal: "uncia Romana." In the seventeenth century, determining the exact weights of antiquity was vital for comparing scientific results across Europe.. This was pointed out to me by the most noble Lord du Verdus. This ounce, like our own French ounce, is divided into 24 deniersoriginal: "denarios." Here used as a unit of weight rather than a coin., and the denier into 24 grains. It is now certain what I proposed as a doubt in point nine of the general Preface. Therefore, there are only 16 copper plates in an ounce. These were mentioned in the first corollary of proposition 3 on numbers, and at the bottom of page 38. I will discuss all these matters more accurately in Rome, God willing. See point three of the corrected errors.

TREATISES CONTAINED

IN THIS VOLUME

I. On Hebrew, Greek, and Roman Measures, Weights, and Coins reduced to French standards.

II. On Hydraulic-pneumatic Phenomena.

III. On the Nautical Art, or Sailing, and Hydrostatics.

IV. On Theoretical and Practical Music.

V. On Mechanical Phenomena.

VI. On Ballistics, or the Phenomena of Projectiles.