Why did lincoln say that he had no intention to "interfere with the institution of slavery"?

the lines on a surface map are called isobars. isobars are lines of constant pressure which are measured in units called millibars. the numbers indicate the amount of air pressure, in millibars, that each line represents.

he said they would ensure there dominace in the new world meaning anyone who lived there and anyone there would be controlled by columbus as he would dominate the country and defeat them by being the biggest empire in the new world