This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1846 edition. Excerpt: ...called the radius vector, in one minute of time, is equal to half the product of the angle Ps o. by the square of the distance s P. And if this product be the same in every portion of the earth's orbit, it follows. that the area swept over by the radius vector of the earth in every minute is the same, and therefore the area swept over in 60 minutes in one part of the orbit, is the same as that swept over in 60 minutes of any other portion of the orbit, and thus that the space or area swept over by the radius vector in one hour, in one day, or one week or month, in any one portion of the earth's orbit, is the same as the area swept over in any other.