Co-ordinate clauses or sentences, especially if not joined by Conjunctions, are generally separated by semi-colons.
Examples of the use of semi-colons.
The first in loftiness of mind surpassed;
The next in majesty; in both the last.—Dryden.
Many a man lives a burden to the earth; but a good book is the precious life-blood of a master-spirit, embalmed and treasured up on purpose to a life beyond life.—Milton.
All nature is but art unknown to thee;
All chance, direction, which thou canst not see;
All discord, harmony, not understood;
All partial evil universal good.—Pope.