The properties of objects have been explained in the Rig Veda. In the Yajurveda is laid down the way of paractical application of the objects of known properties to different arts and acts of utility. In the Sama Veda we are required to bestow deep thought on the mutual relations of knowledge and action in order to arrive at their final results. The Atharvaveda lays down the ways of preserving and improving the science of the final results of knowledge imparted in the three Vedas by giving it final and finishing touches. These are some to the reasons for the division of the Vedas into 4 parts.