The base layer isn't really supposed to be dry. It transfers moisture from your skin and soaks it up. Works sort of like evaporate air conditioning systems houses in the desert have. It soaks up your sweat and the air flowing through gets cooled by the moisture so your skin gets cooler. All you really need to know is you will feel cooler and your core body temp will be lower if you wear a baselayer. If you're looking for even more scientific stuff I can't help you.